This commit replaces the version number 5.5 with 6.0, because 5.5 has never been released. This is a follow-up to https://github.com/scylladb/scylladb/pull/16716. Refs https://github.com/scylladb/scylladb/issues/16551 Refs https://github.com/scylladb/scylladb/issues/18580 Closes scylladb/scylladb#18730