release_notes: please document release notes merging
Originally created by @CyrilBrulebois on #16586 (Redmine)
With previous releases, sajolida was helpful pointing me to the branch with release notes, so that it gets merged in time. I think there are not mentioned at all (except for reproducibility debugging — way before, and tweeting — way after), and it would be great to mention merging that branch right before or after the “Numerous_security_holes_in_[…]” section, so that they aren’t forgotten by anyone.