Merge pull request #55396 from sttts/sttts-drop-deepcopy-registration

Automatic merge from submit-queue. If you want to cherry-pick this change to another branch, please follow the instructions <a href="https://github.com/kubernetes/community/blob/master/contributors/devel/cherry-picks.md">here</a>.

deepcopy: remove unused deepcopy func registration

Counterpart to kubernetes/gengo#67.

Kubernetes-commit: 7c8596a95fb37e3c1318e25ae505989122bd4e56