fix: swapped _R_co and _P to prevent type error.

[TresYap]

When loading a pytorch-lightning model from MLFlow, I get TypeError: Type parameter +_R_co without a default follows type parameter with a default. This happens whenever doing import pytorch_lightning as pl which is done by packages like MLFlow.

What does this PR do?

Fixes #<issue_number>

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📚 Documentation preview 📚: https://pytorch-lightning--20508.org.readthedocs.build/en/20508/

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 79%. Comparing base (9177ec0) to head (37e25f3).

❗ There is a different number of reports uploaded between BASE (9177ec0) and HEAD (37e25f3). Click for more details.

HEAD has 539 uploads less than BASE

Flag	BASE (9177ec0)	HEAD (37e25f3)
gpu	5	0
pytest	76	0
lightning_fabric	21	0
lightning	109	18
cpu	143	24
python3.9	36	6
python3.11	36	6
python3.10	18	3
python3.12.7	53	9
pytorch2.1	27	9
pytest-full	72	24
pytorch2.2.2	9	3
pytorch2.3	9	3
pytorch_lightning	18	6
pytorch2.4.1	9	3
pytorch2.5.1	18	6

Additional details and impacted files

@@            Coverage Diff            @@
##           master   #20508     +/-   ##
=========================================
- Coverage      88%      79%     -9%     
=========================================
  Files         267      264      -3     
  Lines       23380    23325     -55     
=========================================
- Hits        20481    18366   -2115     
- Misses       2899     4959   +2060