[functorch] test no warning on `import functorch` (#85980)
Copied from
https://github.com/pytorch/pytorch/blob/24adadd4dbcd90b5aba1d4a45847e4ffa83bd6cc/test/test_testing.py#L1808
Pull Request resolved: https://github.com/pytorch/pytorch/pull/85980
Approved by: https://github.com/samdow
