Copy branch protections rather than renaming the pattern

[mheap]

https://github.com/mheap/github-default-branch/issues/4#issuecomment-646299374

I think you have the feature to keep the previous branch around. So maybe it should not be an update of the pattern, but a copy of the settings?

If we skip deleting the old branch (using --skip-delete-old-branch), we should copy the settings instead of updating the protection to point at our new branch