Remove implicit loss function conversion in LossPhysical

[Jubeku]

Description

Originally we converted mse loss to mse_channel_location_weighted in LossPhysical.
As mse_channel_location_weighted calculates the non-weighted mse if no weights are given, this PR renames mse_channel_location_weighted to mse and removes the old mse function.

Issue Number

Closes #1536

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Checklist before asking for review

• I have performed a self-review of my code
• My changes comply with basic sanity checks:
  • I have fixed formatting issues with ./scripts/actions.sh lint
  • I have run unit tests with ./scripts/actions.sh unit-test
  • I have documented my code and I have updated the docstrings.
  • I have added unit tests, if relevant
• I have tried my changes with data and code:
  • I have run the integration tests with ./scripts/actions.sh integration-test
  • (bigger changes) I have run a full training and I have written in the comment the run_id(s): launch-slurm.py --time 60
  • (bigger changes and experiments) I have shared a hegdedoc in the github issue with all the configurations and runs for this experiments
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