Remove @FrameworkAgnostic Markers

[killianlevacher]

Is your feature request related to a problem? Please describe. Now that we are using github actions and are no longer limited by the Travis time limit, I would suggest perhaps to remove all the @FrameworkAgnostic Markers from the tests and make sure each of these tests are ran in the relevant frameworks.

The benefit of doing this, is that on top of guaranteeing that each framework agnostic test is indeed framework agnostic (there's been cases in which we were surprised they were not), this would simplify the creation of the test for newbies as this will remove one more possible marker that the would need to consider putting or not on their tests.