Run the pr-label check on PR closed action and validate closed_by (#71917)
Summary:
Fixes https://github.com/pytorch/pytorch/issues/68459
Pull Request resolved: https://github.com/pytorch/pytorch/pull/71917
Reviewed By: malfet
Differential Revision: D33820822
Pulled By: atalman
fbshipit-source-id: 373ffcbc2bcae4041f7f84a4883c086a61afd03b
(cherry picked from commit 2c2c81a9850a8f43397e725a1ec2c593edc66fab)
