Remove references to old datamodule config parameters

[Sukh-P]

Pull Request

Description

Removing references in the example config files to old datamodule config parameters (n_train_data and n_val_data) which are no longer used in the datamodule class (limiting number of batches is done through the trainer config parameters instead i.e limit_train_batches)

This is to make it slightly clearer when looking at the examples what parameters are still in use.

Checklist:

• [ ] My code follows OCF's coding style guidelines
• [ ] I have performed a self-review of my own code
• [X] I have made corresponding changes to the documentation
• [ ] I have added tests that prove my fix is effective or that my feature works
• [ ] I have checked my code and corrected any misspellings

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 61.47%. Comparing base (27f16c5) to head (cc75c26).

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #163 +/- ## ======================================= Coverage 61.47% 61.47% ======================================= Files 28 28 Lines 1786 1786 ======================================= Hits 1098 1098 Misses 688 688 ```

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