[SPARK-18447][DOCS] Fix the markdown for `Note:`/`NOTE:`/`Note that` across Python API documentation

## What changes were proposed in this pull request?

It seems in Python, there are

- `Note:`
- `NOTE:`
- `Note that`
- `.. note::`

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

**Before**

<img width="567" alt="2016-11-21 1 18 49" src="https://cloud.githubusercontent.com/assets/6477701/20464305/85144c86-af88-11e6-8ee9-90f584dd856c.png">

<img width="617" alt="2016-11-21 12 42 43" src="https://cloud.githubusercontent.com/assets/6477701/20464263/27be5022-af88-11e6-8577-4bbca7cdf36c.png">

**After**

<img width="554" alt="2016-11-21 1 18 42" src="https://cloud.githubusercontent.com/assets/6477701/20464306/8fe48932-af88-11e6-83e1-fc3cbf74407d.png">

<img width="628" alt="2016-11-21 12 42 51" src="https://cloud.githubusercontent.com/assets/6477701/20464264/2d3e156e-af88-11e6-93f3-cab8d8d02983.png">

## How was this patch tested?

The notes were found via

```bash
grep -r "Note: " .
grep -r "NOTE: " .
grep -r "Note that " .
```

And then fixed one by one comparing with API documentation.

After that, manually tested via `make html` under `./python/docs`.

Author: hyukjinkwon <gurwls223@gmail.com>

Closes #15947 from HyukjinKwon/SPARK-18447.

1 files changed, 4 insertions, 4 deletions

diff --git a/python/pyspark/ml/clustering.py b/python/pyspark/ml/clustering.py
index e58ec1e7ac..b29b5ac70e 100644
--- a/python/pyspark/ml/clustering.py
+++ b/python/pyspark/ml/clustering.py
@@ -155,7 +155,7 @@ class GaussianMixture(JavaEstimator, HasFeaturesCol, HasPredictionCol, HasMaxIte
     While this process is generally guaranteed to converge, it is not guaranteed
     to find a global optimum.
 
-    Note: For high-dimensional data (with many features), this algorithm may perform poorly.
+    .. note:: For high-dimensional data (with many features), this algorithm may perform poorly.
           This is due to high-dimensional data (a) making it difficult to cluster at all
           (based on statistical/theoretical arguments) and (b) numerical issues with
           Gaussian distributions.
@@ -749,9 +749,9 @@ class DistributedLDAModel(LDAModel, JavaMLReadable, JavaMLWritable):
         If using checkpointing and :py:attr:`LDA.keepLastCheckpoint` is set to true, then there may
         be saved checkpoint files.  This method is provided so that users can manage those files.
 
-        Note that removing the checkpoints can cause failures if a partition is lost and is needed
-        by certain :py:class:`DistributedLDAModel` methods.  Reference counting will clean up the
-        checkpoints when this model and derivative data go out of scope.
+        .. note:: Removing the checkpoints can cause failures if a partition is lost and is needed
+            by certain :py:class:`DistributedLDAModel` methods.  Reference counting will clean up
+            the checkpoints when this model and derivative data go out of scope.
 
         :return  List of checkpoint files from training
         """