This commit removes the invalid information about
the recommended way of upgrading ScyllaDB
images (by updating ScyllaDB and OS packages
in one step) from the 4.6-to-5.0 upgrade guide.
This upgrade procedure is not supported (it was
implemented, but then reverted).
Refs https://github.com/scylladb/scylladb/issues/15733
(cherry picked from commit 526d543b95)