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/y2023/vision/game_pieces.h b/y2023/vision/game_pieces.h
index 442d95c..45bf894 100644
--- a/y2023/vision/game_pieces.h
+++ b/y2023/vision/game_pieces.h
@@ -6,8 +6,7 @@
 #include "y2023/vision/game_pieces_generated.h"
 #include "y2023/vision/yolov5.h"
 
-namespace y2023 {
-namespace vision {
+namespace y2023::vision {
 
 using namespace frc971::vision;
 
@@ -23,6 +22,5 @@
   aos::Sender<GamePieces> game_pieces_sender_;
   std::unique_ptr<YOLOV5> model;
 };
-}  // namespace vision
-}  // namespace y2023
+}  // namespace y2023::vision
 #endif