Dice score average = macro default

[Isalia20]

What does this PR do?

Fixes #3031
This PR should be merged for the release after the next release. First this one should be released:
#3041 and for the next release this PR should be merged

• Was this discussed/agreed via a Github issue? (no need for typos and docs improvements)
• Did you read the contributor guideline, Pull Request section?

---

📚 Documentation preview 📚: https://torchmetrics--3042.org.readthedocs.build/en/3042/

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 35%. Comparing base (4fb185f) to head (f68242b).
⚠️ Report is 1 commits behind head on master.

❗ There is a different number of reports uploaded between BASE (4fb185f) and HEAD (f68242b). Click for more details.

HEAD has 132 uploads less than BASE

Flag	BASE (4fb185f)	HEAD (f68242b)
torch2.0.1+cpu	9	3
python3.10	33	11
Windows	6	2
cpu	48	16
macOS	9	3
torch2.0.1	6	2
torch2.7.1	3	1
python3.12	12	4
torch2.7.1+cpu	9	3
Linux	33	11
torch2.6.0+cpu	6	2
torch2.3.1+cpu	3	1
python3.9	3	1
torch2.1.2+cpu	3	1
torch2.4.1+cpu	3	1
torch2.5.1+cpu	3	1
torch2.2.2+cpu	3	1
gpu	2	0
unittest	2	0

Additional details and impacted files

@@           Coverage Diff            @@
##           master   #3042     +/-   ##
========================================
- Coverage      70%     35%    -36%     
========================================
  Files         364     349     -15     
  Lines       20100   19905    -195     
========================================
- Hits        14123    6894   -7229     
- Misses       5977   13011   +7034     

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[SkafteNicki]

Going to block this to make sure it is not merged by accident too early

[Borda]

@SkafteNicki so when this shall be merged?

[SkafteNicki]

@SkafteNicki so when this shall be merged?

Marked it for v1.9 release

released