Remove some `#ifdef WITH_ANIM_BAKLAVA` guards to make a unit test
succeed. The code is handling slots when assigning Actions to IDs.
Non-experimental builds will only deal with legacy Actions, and thus the
slot assignment is a no-op anyway.
The unit test is explicitly creating layered Actions and running tests
on them. Since this also covers some new code introduced for Action
assignments (unified code for both legacy & layered Actions), I'd feel
more comfortable keeping the test enabled.
Note that when loading a blend file with layered Actions in a
non-experimental build will actually load them as legacy Actions.
Pull Request: https://projects.blender.org/blender/blender/pulls/128483