Remove NeptuneLogger integration from PyTorch Lightning (#21572)

* Remove NeptuneLogger integration from PyTorch Lightning

- Deleted NeptuneLogger from the logger initialization and related files.
- Updated documentation and tests to reflect the removal of NeptuneLogger.
- Adjusted logger-related code to ensure compatibility without NeptuneLogger.

* keep `NeptuneLogger` class as a wrapper and raise an error suggesting litlogger instead

* update

* update

* Update src/lightning/pytorch/loggers/neptune.py

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Co-authored-by: Bhimraj Yadav <bhimrajyadav977@gmail.com>
Co-authored-by: Justus Schock <12886177+justusschock@users.noreply.github.com>