Remove map_msgs exported dependency (#524)

* This is unused

Signed-off-by: Ryan Friedman <[email protected]>

Author: Ryanf55

grid_map_rviz_plugin/CMakeLists.txt

@@ -136,7 +136,6 @@ ament_export_dependencies(
   Qt5
   rviz_common
   geometry_msgs
-  map_msgs
   nav_msgs
   rclcpp
 )