Update Mish to default PyTorch 1.9 version

[digantamisra98]

Description

Update Mish to use the default in PyTorch 1.9

Status

Ready

Types of changes

• Non-breaking change (fix or new feature that would not break existing functionality).
• New tests added to cover the changes.
• Integration tests passed locally by running ./runtests.sh -f -u --net --coverage.
• Quick tests passed locally by running ./runtests.sh --quick --unittests.
• In-line docstrings updated.
• Documentation updated, tested make html command in the docs/ folder.

[Nic-Ma]

Hi @digantamisra98 ,

Thanks for your contribution here.
I think you can use some existing MONAI utilises to simplify:
https://github.com/Project-MONAI/MONAI/blob/dev/monai/utils/module.py#L362

Thanks.

[wyli]

/black

[digantamisra98]

@Nic-Ma Sorry checked back on this late, looks like @wyli has addressed the changes. Thanks a ton for the same.

[madil90]

/build