[complex] Enable complex autograd tests for `diag` (#51268)
Summary:
Reference: https://github.com/pytorch/pytorch/issues/33152
Pull Request resolved: https://github.com/pytorch/pytorch/pull/51268
Reviewed By: pbelevich
Differential Revision: D26179236
Pulled By: anjali411
fbshipit-source-id: e9756136eaaced5a8692228a158965f77505e7b9
