Deprecate/change kl divergence input order

[SkafteNicki]

What does this PR do?

Fixes #2369

Before submitting

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• Did you make sure to update the docs?
• Did you write any new necessary tests?

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📚 Documentation preview 📚: https://torchmetrics--2370.org.readthedocs.build/en/2370/

[codecov]

Codecov Report

Merging #2370 (ea78e2d) into master (f4ef8a8) will increase coverage by 0%.
The diff coverage is 75%.

Additional details and impacted files

@@          Coverage Diff           @@
##           master   #2370   +/-   ##
======================================
  Coverage      69%     69%           
======================================
  Files         305     305           
  Lines       17186   17190    +4     
======================================
+ Hits        11846   11849    +3     
- Misses       5340    5341    +1