fix: sphinx docs build error due to warnings

[bhimrazy]

What does this PR do?

Fixes docs build in master branch.

WARNING: py:data reference target not found: typing.Union
--
build finished with problems, 582 warnings.
make: *** [Makefile:31: html] Error 1

ref: https://github.com/Lightning-AI/torchmetrics/actions/runs/18839686293/job/53748746696

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?

PR review

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📚 Documentation preview 📚: https://torchmetrics--3306.org.readthedocs.build/en/3306/

[Borda]

build HTML is still failing: https://github.com/Lightning-AI/torchmetrics/actions/runs/19759714343/job/56757882195?pr=3306

[bhimrazy]

build HTML is still failing: https://github.com/Lightning-AI/torchmetrics/actions/runs/19759714343/job/56757882195?pr=3306

yes @Borda , the failure seems related with CI spacing.

do we need to clear some cache or try something else to fix this?

[Borda]

we need to clear some cache or try something else to fix this?

You can nuke the cache and prove that the cache is the problem, you can just disable it in the workflow

[bhimrazy]

Finally, the failing build issue is resolved. 🚀

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 37%. Comparing base (88bca94) to head (2d929a5).

❌ Your project check has failed because the head coverage (37%) is below the target coverage (95%). You can increase the head coverage or adjust the target coverage.

Additional details and impacted files

@@           Coverage Diff           @@
##           master   #3306    +/-   ##
=======================================
- Coverage      37%     37%    -1%     
=======================================
  Files         364     349    -15     
  Lines       20096   19901   -195     
=======================================
- Hits         7520    7326   -194     
+ Misses      12576   12575     -1     

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Pull request overview

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