Add missing headers (#486)

Signed-off-by: Jenn Nguyen <jenn@openrobotics.org>
Co-authored-by: Steve Peters <scpeters@openrobotics.org>

Author: jennuine

examples/standalone/point_cloud/point_cloud.cc

@@ -18,6 +18,8 @@
 #include <gz/msgs/float_v.pb.h>
 #include <gz/msgs/pointcloud_packed.pb.h>
 
+#include <gz/msgs/PointCloudPackedUtils.hh>
+#include <gz/msgs/Utility.hh>
 #include <gz/transport/Node.hh>
 
 #include <atomic>