Update describe.py
Updated the code to exclude 0.5 percentile

Excluded the 0.5 percentile from the code where a value is passed.

Added a test case to validate if 0.5 percentile is excluded or not

As mentioned before, you have an open pull request in https://github.com/pandas-dev/pandas/pull/60986 and we prefer you update that pull request with updates.

If you need guidance on how to do that see https://pandas.pydata.org/docs/development/contributing.html#updating-your-pull-request. Closing this PR in favor of your old one