docs: fix MD links

[Borda]

What does this PR do?

some dead links

Before submitting

• Was this discussed/agreed via a Github issue? (no need for typos and docs improvements)
• Did you read the contributor guideline, Pull Request section?
• Did you make sure to update the docs?
• Did you write any new necessary tests?

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📚 Documentation preview 📚: https://torchmetrics--2098.org.readthedocs.build/en/2098/

[codecov]

Codecov Report

Merging #2098 (7c65652) into master (809bb5f) will not change coverage.
The diff coverage is n/a.

Additional details and impacted files

@@          Coverage Diff           @@
##           master   #2098   +/-   ##
======================================
  Coverage      87%     87%           
======================================
  Files         293     293           
  Lines       16299   16299           
======================================
  Hits        14177   14177           
  Misses       2122    2122