docs: enable Sphinx nitpicky

[Borda]

What does this PR do?

nitpicky
If true, Sphinx will warn about all references where the target cannot be found. Default is False. You can activate this mode temporarily using the -n command-line switch.

ref: optuna/optuna#4213

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• Was this discussed/agreed via a Github issue? (no need for typos and docs improvements)
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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--1916.org.readthedocs.build/en/1916/

[Borda]

So not sure how to tell sphinx mapping also, this just built package... :/

[Borda]

also these seem to be missing WARNING: py:class reference target not found: torch.FloatTensor

[codecov]

Codecov Report

Merging #1916 (c9c3afc) into master (23356d4) will not change coverage.
The diff coverage is 100%.

Additional details and impacted files

@@          Coverage Diff           @@
##           master   #1916   +/-   ##
======================================
  Coverage      87%     87%           
======================================
  Files         268     268           
  Lines       15427   15427           
======================================
  Hits        13360   13360           
  Misses       2067    2067           

[Borda]

Ok, checked some and seems some links are really wrong so need to get fixed...

[Borda]

lets wait for #1956 and #1958

[Borda]

THANK YOU @SkafteNicki 💜 only 177 left... and remarkable finding with #1998