doc: remove outdated JMX references
This commit removes references to JMX from the docs.
Context:
The JMX server has been dropped and removed from installation. The user can
install it manually if needed, as documented with https://github.com/scylladb/scylladb/issues/18687.
This commit removes the outdated information about JMX from other pages
in the documentation, including the docs for nodetool, the list of ports,
and the admin section.
Also, the no longer relevant JMX information is removed from
the Docker Hub docs.
Fixes https://github.com/scylladb/scylladb/issues/18687
Fixes https://github.com/scylladb/scylladb/issues/19575
(cherry picked from commit 4e43d542cd)
Closes scylladb/scylladb#20988
1d11adf766