[JIT] enable autocasting + freezing test
Test was marked as `skip` due ot a memory leak. Turns out the memory leak is expected - it can be fixed by clearing the compilation unit (with `torch.jit._state._python_cu.drop_all_functions()` at the end of the test function) or by disabling the leak detector on this test.
Fixes #77618
Pull Request resolved: https://github.com/pytorch/pytorch/pull/78566
Approved by: https://github.com/eellison
