DOC: Fix docstrings for Timestamp: unit, utcoffset, utctimetuple
Part of https://github.com/pandas-dev/pandas/issues/59458

Addresses:

pandas.Timestamp.unit having SA01
pandas.Timestamp.utcoffset having SA01
pandas.Timestamp.utctimetuple having SA01

Changes:
Added See Also section for all 3.
Added Returns section for all 3.
Added extended section for all 3
Removed all 3 from code_checks.sh
Thanks @shreyas-dev 