Description
From @David-Engel:
Looking at the history, it looks like I started the pattern. But I think it was because my initial release notes for 1.x were in 1.x.md instead of 1.x.x.md. I had linked to 1.0.md and 1.1.md in announcements and didn't want to delete the file/break the links. Once we started servicing, new 1.x.x.md files were added and the 1.x.md files changed to summaries. The file pattern has been replicated since then.
I haven't linked to the x.x.md files in years, so I say just break the pattern going forward. Even for 5.1, it should be fine to delete 5.1.md. Just don't bother for out of support versions.
We can remove these files whose contents duplicates the X.Y/README.md files. Ensure any content in the X.Y.md files that isn't in the README.md files gets merged in before removing them.
Do this only for the in-service branches, currently 5.1, 5.2, 6.0, main.