This reverts commit f60c94fc16.
Reason for revert: This introduced a bug:
https://cert-manager.io/docs/installation/upgrading/upgrading-0.15-0.16/#issue-with-older-versions-of-kubectl
Older versions of kubectl will have issues with the nested CRDs.
Change-Id: I322fc1382fe3d0a4517e4c7c5982ea50a721a1f7