This commit adds the information that the manual recovery procedure
is not supported if tablets are enabled.
In addition, the content in the Manual Recovery Procedure is reorganized
by adding the Prerequisites and Procedure subsections - in this way,
we can limit the number of Note and Warning boxes that made the page
hard to follow.
Fixes https://github.com/scylladb/scylladb/issues/18895Closesscylladb/scylladb#18935