[SPARK-54604][PYTHON][DOCS] Fix grammar issues in python_data_source.rst

### What changes were proposed in this pull request?
Fixes a few grammar issues in `python_data_source.rst`.

"that generate" → "that generates"
"has a integer" → "has an integer"
"that increase" → "that increases"

### Why are the changes needed?
Fix grammar for user facing docs.

### Does this PR introduce _any_ user-facing change?
updated docs.

### How was this patch tested?
doc test

### Was this patch authored or co-authored using generative AI tooling?
No

Closes #53337 from Yicong-Huang/SPARK-54603/fix/grammar-issues.

Authored-by: Yicong-Huang <17627829+Yicong-Huang@users.noreply.github.com>
Signed-off-by: Hyukjin Kwon <gurwls223@apache.org>

Author: Yicong-Huang

python/docs/source/tutorial/sql/python_data_source.rst

@@ -219,7 +219,7 @@ Create a fake data source writer that processes each partition of data, counts t
 Implement a Streaming Reader
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 
-This is a dummy streaming data reader that generate 2 rows in every microbatch. The streamReader instance has a integer offset that increase by 2 in every microbatch.
+This is a dummy streaming data reader that generates 2 rows in every microbatch. The streamReader instance has an integer offset that increases by 2 in every microbatch.
 
 .. code-block:: python
 
@@ -291,7 +291,7 @@ One of simpleStreamReader() and streamReader() must be implemented for a readabl
 
         ...
 
-This is the same dummy streaming reader that generate 2 rows every batch implemented with SimpleDataSourceStreamReader interface.
+This is the same dummy streaming reader that generates 2 rows every batch implemented with SimpleDataSourceStreamReader interface.
 
 .. code-block:: python