[SPARK-54065][PYTHON][TESTS][FOLLOWUP] Remove unused import module from test_python_datasource.py

### What changes were proposed in this pull request?
This PR aims to recover CI by removing `import sys` from `test_python_datasource.py`
After #52967, CI consistently fails because `sys` is no longer used.

### Why are the changes needed?
To recover CI.

### Does this PR introduce _any_ user-facing change?
No.

### How was this patch tested?
GA.

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

Closes #52970 from sarutak/followup-SPARK-54065.

Authored-by: Kousuke Saruta <sarutak@amazon.co.jp>
Signed-off-by: Ruifeng Zheng <ruifengz@apache.org>

Author: sarutak

python/pyspark/sql/tests/test_python_datasource.py

@@ -16,7 +16,6 @@
 #
 import os
 import platform
-import sys
 import tempfile
 import unittest
 import logging