Fix: Set default average='micro' consistently across classification metrics (some of the subclasses of MulticlassStatScores, MultilabelStatScores)

[rittik9]

What does this PR do?

Partially Fixes #2320

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

Anyone in the community is free to review the PR once the tests have passed.
If we didn't discuss your PR in Github issues there's a high chance it will not be merged.

Changed the doctest values for subclasses of MulticlassStatScores, MultilabelStatScores for average = 'micro' as earlier default value was average = 'macro'

Did you have fun?

Make sure you had fun coding 🙃

---

📚 Documentation preview 📚: https://torchmetrics--2882.org.readthedocs.build/en/2882/

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 41%. Comparing base (767c678) to head (d19a1eb).

❌ Your project check has failed because the head coverage (41%) is below the target coverage (95%). You can increase the head coverage or adjust the target coverage.

❗ There is a different number of reports uploaded between BASE (767c678) and HEAD (d19a1eb). Click for more details.

HEAD has 4 uploads less than BASE

Flag	BASE (767c678)	HEAD (d19a1eb)
gpu	2	0
unittest	2	0

Additional details and impacted files

@@           Coverage Diff            @@
##           master   #2882     +/-   ##
========================================
- Coverage      69%     41%    -28%     
========================================
  Files         346     332     -14     
  Lines       19172   18996    -176     
========================================
- Hits        13236    7742   -5494     
- Misses       5936   11254   +5318     

[Borda]

I undestand the mostivation and it sounds good at fist look, just for the context we tried to have the same default behavior as SK-learn so that is wy we do not have the same averaging everywhere... but open to chat about it and eventually make this breaking change...

cc: @lantiga @SkafteNicki