Fix mixed results of rouge_score with accumulate='best'

[rittik9]

What does this PR do?

Fixes #2148

Before submitting

• Was this discussed/agreed via a Github issue? (no need for typos and docs improvements)
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• Did you make sure to update the docs?
• Did you write any new necessary tests?

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📚 Documentation preview 📚: https://torchmetrics--2830.org.readthedocs.build/en/2830/

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 39%. Comparing base (ea29c89) to head (6959b79).
Report is 1 commits behind head on master.

❗ There is a different number of reports uploaded between BASE (ea29c89) and HEAD (6959b79). Click for more details.

HEAD has 168 uploads less than BASE

Flag	BASE (ea29c89)	HEAD (6959b79)
macOS	12	3
cpu	56	14
python3.12	12	3
torch2.5.0	4	1
torch2.0.1+cpu	12	3
python3.10	36	9
Windows	8	2
torch2.5.0+cpu	4	1
torch2.0.1	8	2
Linux	36	9
python3.11	4	1
torch2.4.1+cu121	8	2
torch2.2.2+cpu	4	1
torch2.3.1+cpu	4	1
python3.9	4	1
torch2.1.2+cpu	4	1
torch2.5.0+cu124	8	2

Additional details and impacted files

@@           Coverage Diff            @@
##           master   #2830     +/-   ##
========================================
- Coverage      69%     39%    -30%     
========================================
  Files         330     330             
  Lines       18795   18793      -2     
========================================
- Hits        12942    7306   -5636     
- Misses       5853   11487   +5634