DOC: Add DataFrame.median() to the deprecated automatic downcasting list in release notes 2.2.0

- [ ] closes #xxxx (Replace xxxx with the GitHub issue number)
- [ ] [Tests added and passed](https://pandas.pydata.org/pandas-docs/dev/development/contributing_codebase.html#writing-tests) if fixing a bug or adding a new feature
- [ ] All [code checks passed](https://pandas.pydata.org/pandas-docs/dev/development/contributing_codebase.html#pre-commit).
- [ ] Added [type annotations](https://pandas.pydata.org/pandas-docs/dev/development/contributing_codebase.html#type-hints) to new arguments/methods/functions.
- [ ] Added an entry in the latest `doc/source/whatsnew/vX.X.X.rst` file if fixing a bug or adding a new feature.

In version 2.1.4, the median function in pandas automatically performed downcasting from object to float64. However, in version 2.2.0, this automatic downcasting no longer occurs. Thanks for the pull request, but the project does not unfortunately update old release notes. Sorry for this over site when originally crafting these release notes but closing this PR