Revert "DEPR: Deprecate returning a DataFrame in SeriesApply.apply_standard
Reasons for reverting:

- This was done for performance reasons, but this kills the use case to unpack nested data (lists for example)
- The deprecation is poorly done (axis 1 does not emit a warning)
- There is no documentation what users should do, this is necessary if we deprecate something for performance reasons

#52116

closes #55134
I'm okay with reverting this for now. Could you link any related open user issues (if available)?

Also might be worth adding a unit test for unpacking nested data with apply.

cc @topper-123  Added a test and linked the issue in the top post Thanks @phofl. This deprecation is probably highly relevant in the PDEP 13 discussion  yep agree