[SPARK-51078][SPARK-50963][ML][PYTHON][CONNECT][TESTS][FOLLOW-UP] Add back tests for default value

### What changes were proposed in this pull request?
add back tests deleted in e0a7db2#diff-50e109673576cc6d4f8727f54076b0884b93b759c49d98c908581db7093cb5ab

### Why are the changes needed?
for coverage, `StopWordRemover`'s default value implementation is special

### Does this PR introduce _any_ user-facing change?
no

### How was this patch tested?
ci

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

Closes #50067 from zhengruifeng/ml_connect_test_swr.

Authored-by: Ruifeng Zheng <[email protected]>
Signed-off-by: Ruifeng Zheng <[email protected]>
(cherry picked from commit 7e5bf72)
Signed-off-by: Ruifeng Zheng <[email protected]>

Author: zhengruifeng

python/pyspark/ml/tests/test_feature.py

@@ -891,6 +891,8 @@ def test_stop_words_remover_with_given_words(self):
         self.assertEqual(stopWordRemover.getInputCol(), "input")
         transformedDF = stopWordRemover.transform(dataset)
         self.assertEqual(transformedDF.head().output, ["panda"])
+        self.assertEqual(type(stopWordRemover.getStopWords()), list)
+        self.assertTrue(isinstance(stopWordRemover.getStopWords()[0], str))
         # Custom
         stopwords = ["panda"]
         stopWordRemover.setStopWords(stopwords)