Adding test for legacy checkpoint created with 2.5.5

[pl-ghost]

This is automated addition of created checkpoint with the latest 2.5.5 lightning release!

cc @lantiga @Borda

[github-actions]

⚡ Required checks status: All passing 🟢

Groups summary

🟢 pytorch_lightning: Tests workflow

Check ID	Status
pl-cpu-guardian	success	✅

These checks are required after the changes to tests/legacy/back-compatible-versions.txt.

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Thank you for your contribution! 💜

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 79%. Comparing base (77f9811) to head (e89cf72).
⚠️ Report is 1 commits behind head on master.

❗ There is a different number of reports uploaded between BASE (77f9811) and HEAD (e89cf72). Click for more details.

HEAD has 117 uploads less than BASE

Flag	BASE (77f9811)	HEAD (e89cf72)
gpu	3	0
pytest	30	0
lightning_fabric	14	0
cpu	54	27
python	6	3
lightning	31	15
python3.11	12	6
python3.10	12	6
python3.12	6	3
python3.12.7	18	9

Additional details and impacted files

@@            Coverage Diff            @@
##           master   #21168     +/-   ##
=========================================
- Coverage      87%      79%     -8%     
=========================================
  Files         269      266      -3     
  Lines       23656    23601     -55     
=========================================
- Hits        20633    18606   -2027     
- Misses       3023     4995   +1972