ament_export_interfaces: CMake deprecation warnings for foxy

[francocipollone]

CMake Deprecation Warning at /opt/ros/foxy/share/ament_cmake_export_interfaces/cmake/ament_export_interfaces.cmake:37 (message):
  ament_export_interfaces() is deprecated, use ament_export_targets() instead
Call Stack (most recent call first):
  CMakeLists.txt:85 (ament_export_interfaces)

Victory condition

Use ament_export_targets instead of ament_export_interfaces

[francocipollone]

Also, using ament_export_libraries is superflous when using ament_export_targets so it could be avoided for consistency, See here