Improvements based on v21.0.1 (and other) patch releases

[rohit-nayak-ps]

• Show release version even on inner pages. While we show it in the footer of the main menu, once we are on a specific item we don't see it. Since we do multiple versions in patch releases, this will be useful.
• Remove cobra docs sync check for patch releases
• Fix link to docker actions workflow for >= v21

[shlomi-noach]

When the tool creates a pull request, it should include a link to the Release Issue in the pool request's main comment. Examples for pull requests that do not have a link back to the Release Issue:

• [release-21.0] Release of v21.0.1 vitess#17317
• [main] Copy v21.0.1 release notes vitess#17324