Replace deprecated ament_export_interfaces (#1669)

with ament_export_targets
See notice here:
https://index.ros.org/doc/ros2/Releases/Release-Foxy-Fitzroy/

nav2_rviz_plugins/CMakeLists.txt

@@ -112,7 +112,7 @@ if(BUILD_TESTING)
 endif()
 
 ament_export_include_directories(include)
-ament_export_interfaces(${library_name} HAS_LIBRARY_TARGET)
+ament_export_targets(${library_name} HAS_LIBRARY_TARGET)
 ament_export_dependencies(
   Qt5
   rviz_common