This commit updates the migration overview page:
- It removes the info about migration from SSTable to CQL.
- It updates the link to the migrator docs.
Fixes https://github.com/scylladb/scylladb/issues/24247
Refs https://github.com/scylladb/scylladb/pull/21775
Closes scylladb/scylladb#24258
(cherry picked from commit b197d1a617)
Closes scylladb/scylladb#24280