[SPARK-49600][PYTHON] Remove Python 3.6 and older-related logic from try_simplify_traceback

[dongjoon-hyun]

What changes were proposed in this pull request?

Apache Spark 4.0.0 supports only Python 3.9+.

• [SPARK-47993][PYTHON] Drop Python 3.8 #46228

Why are the changes needed?

To simplify and clarify the logic. I manually confirmed that this is the last logic about sys.version_info and (3, 7).

$ git grep 'sys.version_info' | grep '(3, 7)'
python/pyspark/util.py:    if sys.version_info[:2] < (3, 7):
python/pyspark/util.py:    if "pypy" not in platform.python_implementation().lower() and sys.version_info[:2] >= (3, 7):

Does this PR introduce any user-facing change?

No.

How was this patch tested?

Pass the CIs.

Was this patch authored or co-authored using generative AI tooling?

No.

[LuciferYang]

+1, LGTM

[dongjoon-hyun]

Thank you, @LuciferYang .

[dongjoon-hyun]

Merged to master.