Remove the `anim.slot_new_for_object` operator. It's no longer in use, and
replaced by the more generic `anim.slot_new_for_id` operator.
The latter is also coded in Python, and easier to follow than the code it
replaced.
No functional changes.
Pull Request: https://projects.blender.org/blender/blender/pulls/128710
f093e4ad44