Add release version check and stop trying to bump to an RC version

[nmburgan]

This will prevent us from releasing if we forget to merge the PR from prepare_release. This also removes bump_to_rc_after_release since we don't do that in this repo and it would always fail.

Checklist

I have:

• read the CONTRIBUTING.md document
• read and accepted the Developer Certificate of Origin document and added a Signed-off-by annotation to each of my commits
• tested this code
• included documentation (including possible behaviour changes)
• documented the code
• added or modified regression test(s)
• added or modified unit test(s)