This commit updates the documentation about Raft in version 6.0.
- "Introduction": The outdated information about consistent topology updates not being supported
is removed and replaced with the correct information.
- "Enabling Raft": The relevant information is moved to other sections. The irrelevant information
is removed. The section no longer exists.
- "Verifying that the Raft upgrade procedure finished successfully" - moved under Schema
(in the same document). I additionally removed the include saying that after you verify
that schema on Raft is enabled, you MUST enable topology changes on Raft (it is not mandatory;
also, it should be part of the upgrade guide, not the Raft document).
- Unnecessary or incorrect references to versions are removed.
Refs https://github.com/scylladb/scylladb/issues/18580Closesscylladb/scylladb#18689