Fix issue with shared state of MetricCollection compute group when using DiceScore(average="weighted")

[nkaenzig]

What does this PR do?

Fixes #2847

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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Tested using the code snippet provided in the issue description.

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📚 Documentation preview 📚: https://torchmetrics--2848.org.readthedocs.build/en/2848/

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 35%. Comparing base (a968ebe) to head (3132783).
Report is 1 commits behind head on master.

❗ There is a different number of reports uploaded between BASE (a968ebe) and HEAD (3132783). Click for more details.

HEAD has 2 uploads less than BASE

Flag	BASE (a968ebe)	HEAD (3132783)
gpu	1	0
unittest	1	0

Additional details and impacted files

@@           Coverage Diff            @@
##           master   #2848     +/-   ##
========================================
- Coverage      69%     35%    -34%     
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  Files         346     332     -14     
  Lines       19129   18952    -177     
========================================
- Hits        13227    6590   -6637     
- Misses       5902   12362   +6460