Cleaned up test_mps.py::test_output*_match (#108092)
Description:
- cleaned up test_mps.py::test_output_match and test_mps.py::test_output_grad_match tests
- removed unused variables and useless brackets
- simplified atol/rtol setup if/else code
Pull Request resolved: https://github.com/pytorch/pytorch/pull/108092
Approved by: https://github.com/kulinseth
