Simplify Fabric tests workflow matrix

[matsumotosan]

What does this PR do?

Simplify GitHub workflow matrix for Fabric tests (similar to #21132).

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• Did you list all the breaking changes introduced by this pull request?
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📚 Documentation preview 📚: https://pytorch-lightning--21142.org.readthedocs.build/en/21142/

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 48%. Comparing base (6fc44c9) to head (d7142b3).
⚠️ Report is 2 commits behind head on master.

❗ There is a different number of reports uploaded between BASE (6fc44c9) and HEAD (d7142b3). Click for more details.

HEAD has 132 uploads less than BASE

Flag	BASE (6fc44c9)	HEAD (d7142b3)
cpu	51	27
python	6	3
lightning	30	15
python3.11	12	6
python3.10	11	6
python3.12.7	17	9
python3.12	5	3
gpu	3	0
pytorch2.2.2	3	0
pytest-full	27	0
pytorch2.3	3	0
pytorch2.1	6	0
pytorch_lightning	12	0
pytorch2.7	3	0
pytorch2.8	3	0
pytorch2.4.1	3	0
pytorch2.5.1	3	0
pytorch2.6	3	0

Additional details and impacted files

@@            Coverage Diff            @@
##           master   #21142     +/-   ##
=========================================
- Coverage      87%      48%    -39%     
=========================================
  Files         269      266      -3     
  Lines       23560    23504     -56     
=========================================
- Hits        20546    11266   -9280     
- Misses       3014    12238   +9224