[SPARK-18445][BUILD][DOCS] Fix the markdown for `Note:`/`NOTE:`/`Note that`/`'''Note:'''` across Scala/Java API documentation

## What changes were proposed in this pull request?

It seems in Scala/Java,

- `Note:`
- `NOTE:`
- `Note that`
- `'''Note:'''`
- `note`

This PR proposes to fix those to `note` to be consistent.

**Before**

- Scala
  ![2016-11-17 6 16 39](https://cloud.githubusercontent.com/assets/6477701/20383180/1a7aed8c-acf2-11e6-9611-5eaf6d52c2e0.png)

- Java
  ![2016-11-17 6 14 41](https://cloud.githubusercontent.com/assets/6477701/20383096/c8ffc680-acf1-11e6-914a-33460bf1401d.png)

**After**

- Scala
  ![2016-11-17 6 16 44](https://cloud.githubusercontent.com/assets/6477701/20383167/09940490-acf2-11e6-937a-0d5e1dc2cadf.png)

- Java
  ![2016-11-17 6 13 39](https://cloud.githubusercontent.com/assets/6477701/20383132/e7c2a57e-acf1-11e6-9c47-b849674d4d88.png)

## How was this patch tested?

The notes were found via

```bash
grep -r "NOTE: " . | \ # Note:|NOTE:|Note that|'''Note:'''
grep -v "// NOTE: " | \  # starting with // does not appear in API documentation.
grep -E '.scala|.java' | \ # java/scala files
grep -v Suite | \ # exclude tests
grep -v Test | \ # exclude tests
grep -e 'org.apache.spark.api.java' \ # packages appear in API documenation
-e 'org.apache.spark.api.java.function' \ # note that this is a regular expression. So actual matches were mostly `org/apache/spark/api/java/functions ...`
-e 'org.apache.spark.api.r' \
...
```

```bash
grep -r "Note that " . | \ # Note:|NOTE:|Note that|'''Note:'''
grep -v "// Note that " | \  # starting with // does not appear in API documentation.
grep -E '.scala|.java' | \ # java/scala files
grep -v Suite | \ # exclude tests
grep -v Test | \ # exclude tests
grep -e 'org.apache.spark.api.java' \ # packages appear in API documenation
-e 'org.apache.spark.api.java.function' \
-e 'org.apache.spark.api.r' \
...
```

```bash
grep -r "Note: " . | \ # Note:|NOTE:|Note that|'''Note:'''
grep -v "// Note: " | \  # starting with // does not appear in API documentation.
grep -E '.scala|.java' | \ # java/scala files
grep -v Suite | \ # exclude tests
grep -v Test | \ # exclude tests
grep -e 'org.apache.spark.api.java' \ # packages appear in API documenation
-e 'org.apache.spark.api.java.function' \
-e 'org.apache.spark.api.r' \
...
```

```bash
grep -r "'''Note:'''" . | \ # Note:|NOTE:|Note that|'''Note:'''
grep -v "// '''Note:''' " | \  # starting with // does not appear in API documentation.
grep -E '.scala|.java' | \ # java/scala files
grep -v Suite | \ # exclude tests
grep -v Test | \ # exclude tests
grep -e 'org.apache.spark.api.java' \ # packages appear in API documenation
-e 'org.apache.spark.api.java.function' \
-e 'org.apache.spark.api.r' \
...
```

And then fixed one by one comparing with API documentation/access modifiers.

After that, manually tested via `jekyll build`.

Author: hyukjinkwon <gurwls223@gmail.com>

Closes #15889 from HyukjinKwon/SPARK-18437.

4 files changed, 6 insertions, 6 deletions

diff --git a/python/pyspark/mllib/stat/KernelDensity.py b/python/pyspark/mllib/stat/KernelDensity.py
index 3b1c5519bd..7250eab670 100644
--- a/python/pyspark/mllib/stat/KernelDensity.py
+++ b/python/pyspark/mllib/stat/KernelDensity.py
@@ -28,7 +28,7 @@ from pyspark.rdd import RDD
 
 class KernelDensity(object):
     """
-    Estimate probability density at required points given a RDD of samples
+    Estimate probability density at required points given an RDD of samples
     from the population.
 
     >>> kd = KernelDensity()
diff --git a/python/pyspark/mllib/util.py b/python/pyspark/mllib/util.py
index ed6fd4bca4..97755807ef 100644
--- a/python/pyspark/mllib/util.py
+++ b/python/pyspark/mllib/util.py
@@ -499,7 +499,7 @@ class LinearDataGenerator(object):
     def generateLinearRDD(sc, nexamples, nfeatures, eps,
                           nParts=2, intercept=0.0):
         """
-        Generate a RDD of LabeledPoints.
+        Generate an RDD of LabeledPoints.
         """
         return callMLlibFunc(
             "generateLinearRDDWrapper", sc, int(nexamples), int(nfeatures),
diff --git a/python/pyspark/rdd.py b/python/pyspark/rdd.py
index a163ceafe9..641787ee20 100644
--- a/python/pyspark/rdd.py
+++ b/python/pyspark/rdd.py
@@ -1218,7 +1218,7 @@ class RDD(object):
 
     def top(self, num, key=None):
         """
-        Get the top N elements from a RDD.
+        Get the top N elements from an RDD.
 
         Note that this method should only be used if the resulting array is expected
         to be small, as all the data is loaded into the driver's memory.
@@ -1242,7 +1242,7 @@ class RDD(object):
 
     def takeOrdered(self, num, key=None):
         """
-        Get the N elements from a RDD ordered in ascending order or as
+        Get the N elements from an RDD ordered in ascending order or as
         specified by the optional key function.
 
         Note that this method should only be used if the resulting array is expected
diff --git a/python/pyspark/streaming/kafka.py b/python/pyspark/streaming/kafka.py
index bf27d8047a..134424add3 100644
--- a/python/pyspark/streaming/kafka.py
+++ b/python/pyspark/streaming/kafka.py
@@ -144,7 +144,7 @@ class KafkaUtils(object):
         """
         .. note:: Experimental
 
-        Create a RDD from Kafka using offset ranges for each topic and partition.
+        Create an RDD from Kafka using offset ranges for each topic and partition.
 
         :param sc:  SparkContext object
         :param kafkaParams: Additional params for Kafka
@@ -155,7 +155,7 @@ class KafkaUtils(object):
         :param valueDecoder:  A function used to decode value (default is utf8_decoder)
         :param messageHandler: A function used to convert KafkaMessageAndMetadata. You can assess
                                meta using messageHandler (default is None).
-        :return: A RDD object
+        :return: An RDD object
         """
         if leaders is None:
             leaders = dict()