Mention PyREPL is disabled when Python shell integration is enabled for Python3.13 and above

[anthonykim1]

Since shell integration enabled with PyREPL causes cursor indentation issue python/cpython#126131 we should only disable PyREPL and inject the flag to disable PyREPL when user has enabled Python shell integration: #25164

Add documentation in the setting description for Python shell integration that PyREPL(which is available from Python3.13 and above) gets disabled if shell integration for Python is enabled by user.

Otherwise, allow user using Python3.13 and above to use PyREPL and not inject the environment variable to disable PyREPL.

[anthonykim1]

Resolved via #25296