fix: correct the positional encoding of Transformer in pytorch examples

[Galaxy-Husky]

What does this PR do?

Fixes #19138

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📚 Documentation preview 📚: https://pytorch-lightning--20203.org.readthedocs.build/en/20203/

[Galaxy-Husky]

The difference between this example and the original one pytorch example is that the default value of argument batch_first is set to False in PyTorch, whereas here it is set to True.

In order to use the positional encoding correctly, I made the above changes. But I don't know how to write a test case.

[codecov]

Codecov Report

Attention: Patch coverage is 0% with 2 lines in your changes missing coverage. Please review.

Project coverage is 81%. Comparing base (5be58f6) to head (7355f4f).
Report is 81 commits behind head on master.

❗ There is a different number of reports uploaded between BASE (5be58f6) and HEAD (7355f4f). Click for more details.

HEAD has 553 uploads less than BASE

Flag	BASE (5be58f6)	HEAD (7355f4f)
cpu	147	21
lightning	106	16
pytest	87	2
python3.9	43	6
python3.10	42	6
lightning_fabric	25	0
gpu	4	2
python3.11	42	6
python3.12	20	3
pytorch2.1	38	12
pytest-full	64	21
pytorch2.3	9	3
pytorch_lightning	20	7
pytorch2.2	9	3
pytorch2.4	8	3

Additional details and impacted files

@@            Coverage Diff            @@
##           master   #20203     +/-   ##
=========================================
- Coverage      89%      81%     -8%     
=========================================
  Files         267      264      -3     
  Lines       23084    23029     -55     
=========================================
- Hits        20585    18618   -1967     
- Misses       2499     4411   +1912     

[Galaxy-Husky]

@Borda Hi, could you tell me how to deal with the two failed workflows?

[lantiga]

Nice catch!