This PR adds the link to the KB article about updating the mode after the upgrade to the 5.1 upgrade guide.
In addition, I have:
- updated the KB article to include the versions affected by that change.
- fixed the broken link to the page about metric updates (it is not related to the KB article, but I fixed it in the same PR to limit the number of PRs that need to be backported).
Related: https://github.com/scylladb/scylladb/pull/11122Closes#12148
* github.com:scylladb/scylladb:
doc: update the releases in the KB about updating the mode after upgrade
doc: fix the broken link in the 5.1 upgrade guide
doc: add the link to the 5.1-related KB article to the 5.1 upgrade guide
(cherry picked from commit 897b501ba3)