disable-monitoring: run manually only
    
    In the past, after the `retire` function, `disable-monitoring`
    was executed automatically. This functionality wasn't clear for
    users. Now only a manual run is possible.
    Also, more description was added to `disable-monitoring --help` page.
    It should prevent confusion when the operation fails (most likely
    because of a missing token or token with a lower ACL).
    
    JIRA: RHELCMP-11384
    Fixes: #505
    
    Signed-off-by: Ondřej Nosek <onosek@redhat.com>