Remove set_default_dtype calls from jit and ops tests (#105072)
Part of #68972
This only attempts to avoid setting the default dtype for `test_jit.py` and `test_ops.py`. There are other tests, like `test_nn.py`, which will be addressed in follow up PRs
Pull Request resolved: https://github.com/pytorch/pytorch/pull/105072
Approved by: https://github.com/ezyang
