Docs: Remove undocumented zero_division reference from dice_score docstring.

[rittik9]

What does this PR do?

Fixes #3258

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--3279.org.readthedocs.build/en/3279/

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 32%. Comparing base (3eb05bf) to head (4560708).

❌ Your project check has failed because the head coverage (32%) 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 (3eb05bf) and HEAD (4560708). Click for more details.

HEAD has 1140 uploads less than BASE

Flag	BASE (3eb05bf)	HEAD (4560708)
torch2.0.1+cpu	53	3
python3.10	212	12
Windows	35	2
cpu	301	17
torch2.8.0	17	1
macOS	50	3
python3.12	71	4
torch2.8.0+cpu	54	3
torch2.0.1	33	2
Linux	216	12
torch2.7.1+cpu	36	2
gpu	2	0
unittest	2	0
torch2.2.2+cpu	18	1
torch2.6.0+cpu	18	1
torch2.4.1+cpu	18	1
torch2.1.2+cpu	18	1
torch2.3.1+cpu	18	1
torch2.5.1+cpu	18	1
python3.9	18	1

Additional details and impacted files

@@           Coverage Diff            @@
##           master   #3279     +/-   ##
========================================
- Coverage      37%     32%     -5%     
========================================
  Files         364     349     -15     
  Lines       20096   19901    -195     
========================================
- Hits         7520    6376   -1144     
- Misses      12576   13525    +949     

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