[SPARK-36938][PYTHON] Inline type hints for group.py in python/pyspark/sql

[dchvn]

What changes were proposed in this pull request?

Inline type hints for python/pyspark/sql/group.py from Inline type hints for python/pyspark/sql/group.pyi.

Why are the changes needed?

Currently, there is type hint stub files python/pyspark/sql/group.pyi to show the expected types for functions, but we can also take advantage of static type checking within the functions by inlining the type hints.

Does this PR introduce any user-facing change?

No

How was this patch tested?

Existed test.

[SparkQA]

Test build #143880 has finished for PR 34197 at commit b331cc8.

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• This patch adds no public classes.

[SparkQA]

Test build #143878 has finished for PR 34197 at commit 5c732ab.

• This patch passes all tests.
• This patch merges cleanly.
• This patch adds no public classes.

[dchvn]

CC @HyukjinKwon @ueshin @zero323 @xinrong-databricks Please help me review this PR

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Test build #144174 has finished for PR 34197 at commit 514a6f1.

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• This patch adds no public classes.

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Test build #144221 has finished for PR 34197 at commit 6ff504e.

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• This patch merges cleanly.
• This patch adds no public classes.

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[ueshin]

Thanks! merging to master.

[dchvn]

thank you!