Bring back mirroring "enable/disable" checkbox

On gitlab-ee 11.3, the new interface for mirroring no longer has the "mirror repository" checkbox. Our process previously, in some cases, we would disable mirroring between some environments and would re-enable it manually when needed. This option would therefore save all of the information and enable us to push/pull on demand manually.

After the recent UI update, we cannot save the mirroring information unless it is enabled. The only option is to delete and add again later. Would be helpful if we could have the option back to enable/disable.