[shard] fix with_comms wrapper (#69493)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/69493
When added `with_comms` decorator with arguments, we added an `with_comms_decorator` inner function, `with_comms()` will refer to a function object, the added parentheses was necessary to use in test cases.
This PR fixes the `with_comms` wrapper behavior, to allow we both specify with/without arguments in test cases:
```
with_comms
def test_case:
...
```
or
```
with_comms(backend="gloo")
def test_case:
...
```
ghstack-source-id: 145327066
Test Plan: test_sharded_tensor
Reviewed By: pritamdamania87
Differential Revision: D32897555
fbshipit-source-id: 2f3504630df4f6ad1ea73b8084fb781f21604110
