Deprecation of Activity.TYPES attr in model.py

[lwasser]

In the model.py module there is a attr that was added for backward compatibility

    # Added for backward compatibility
    # TODO maybe deprecate?
    TYPES: ClassVar[Tuple[Any, ...]] = get_args(
        ActivityType.__fields__["__root__"].type_
    )

It might be best to deprecate this as discussed here in the review of #387

[lwasser]

this seems like a small issue that one of us would be able to knock out easily! @enadeau you and i had discussed this back in august. Should we remove the types attr in model.py? Strava now favors sport_type over type. But i'm not sure if this will break things or not for some users?