Fix map not showing on rviz when navigation is launched with namespace (

#3620)

nav2_bringup/launch/rviz_launch.py

@@ -71,7 +71,8 @@ def generate_launch_description():
         namespace=namespace,
         arguments=['-d', namespaced_rviz_config_file],
         output='screen',
-        remappings=[('/tf', 'tf'),
+        remappings=[('/map', 'map'),
+                    ('/tf', 'tf'),
                     ('/tf_static', 'tf_static'),
                     ('/goal_pose', 'goal_pose'),
                     ('/clicked_point', 'clicked_point'),