[MINOR] Fix Typos 'an -> a'

## What changes were proposed in this pull request?

`an -> a`

Use cmds like `find . -name '*.R' | xargs -i sh -c "grep -in ' an [^aeiou]' {} && echo {}"` to generate candidates, and review them one by one.

## How was this patch tested?
manual tests

Author: Zheng RuiFeng <ruifengz@foxmail.com>

Closes #13515 from zhengruifeng/an_a.

1 files changed, 2 insertions, 2 deletions

diff --git a/python/pyspark/rdd.py b/python/pyspark/rdd.py
index 411e377a56..6afe769662 100644
--- a/python/pyspark/rdd.py
+++ b/python/pyspark/rdd.py
@@ -1040,7 +1040,7 @@ class RDD(object):
         If the elements in RDD do not vary (max == min) always returns
         a single bucket.
 
-        It will return an tuple of buckets and histogram.
+        It will return a tuple of buckets and histogram.
 
         >>> rdd = sc.parallelize(range(51))
         >>> rdd.histogram(2)
@@ -2211,7 +2211,7 @@ class RDD(object):
         return values.collect()
 
     def _to_java_object_rdd(self):
-        """ Return an JavaRDD of Object by unpickling
+        """ Return a JavaRDD of Object by unpickling
 
         It will convert each Python object into Java object by Pyrolite, whenever the
         RDD is serialized in batch or not.