Avoid using obsolete functions in reset-replication

Removes some duplicate functions.

server/modules/monitor/mariadbmon/mariadbserver.hh

@@ -300,14 +300,6 @@ public:
      */
     bool can_replicate_from(MariaDBServer* master, std::string* reason_out);
 
-    /**
-     * Redirect one slave server to another master
-     *
-     * @param change_cmd Change master command, usually generated by generate_change_master_cmd()
-     * @return True if slave accepted all commands
-     */
-    bool redirect_one_slave(const std::string& change_cmd);
-
     /**
      * Check if the server can be demoted by switchover.
      *