Nest some more namespaces

Did someone previously suggest that all namespace had been
nested?  Silly.

Signed-off-by: Stephan Pleines <pleines.stephan@gmail.com>
Change-Id: I22278c1caaeba8b47dc46fb2ed3078c20a11e190
diff --git a/frc971/vision/visualize_robot.h b/frc971/vision/visualize_robot.h
index c679dba..af2dcef 100644
--- a/frc971/vision/visualize_robot.h
+++ b/frc971/vision/visualize_robot.h
@@ -7,8 +7,7 @@
 #include <opencv2/highgui.hpp>
 #include <opencv2/imgproc.hpp>
 
-namespace frc971 {
-namespace vision {
+namespace frc971::vision {
 
 // Helper class to visualize the coordinate frames associated with
 // the robot Based on a virtual camera viewpoint, and camera model,
@@ -80,7 +79,6 @@
                            // DrawFrameAxes
   cv::Size default_size_;  // Default image size
 };
-}  // namespace vision
-}  // namespace frc971
+}  // namespace frc971::vision
 
 #endif  // FRC971_VISION_VISUALIZE_ROBOT_H_