Deprecate media transformation registration

[wd60622]

Following #1320, there is no need for the registration functions:

• adstock

  pymc-marketing/pymc_marketing/mmm/components/adstock.py

  Lines 332 to 334 in 0764ac4

  	def register_adstock_transformation(cls: type[AdstockTransformation]) -> None:
  	"""Register a new adstock transformation."""
  	ADSTOCK_TRANSFORMATIONS[cls.lookup_name] = cls

• saturation

  pymc-marketing/pymc_marketing/mmm/components/saturation.py

  Lines 462 to 467 in 0764ac4

  	def register_saturation_transformation(cls: type[SaturationTransformation]) -> None:
  	"""Register a new saturation transformation.
  	Helper for use in the MMM to register a new saturation function.
  	"""
  	SATURATION_TRANSFORMATIONS[cls.lookup_name] = cls

It doesn't seem like they are in the documentation. This should be double checked

All references should be removed

[ricor07]

Hello, I'd like to join the project by working on this issue.

[wd60622]

Hello, I'd like to join the project by working on this issue.

Sounds great @ricor07 . That'd be great help!

There are some resources for contributing on the site here

Open a PR as soon as you can (even if in draft state) and we can help you through it!