Remove unused python2 shebang (#58409)
Summary:
This is the only line (not in `third_party`) matching the regex `^#!.*python2`, and [it is not the first line of its file](https://github.com/koalaman/shellcheck/wiki/SC1128), so it has no effect. As a followup to https://github.com/pytorch/pytorch/issues/58275, this PR removes that shebang to reduce confusion, so now all Python shebangs in this repo are `python3`.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/58409
Reviewed By: walterddr
Differential Revision: D28478469
Pulled By: samestep
fbshipit-source-id: c17684c8651e45d3fc383cbbc04a31192d10f52f
