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/control_loops/superstructure/arm/arm.h b/y2023/control_loops/superstructure/arm/arm.h
index 6153400..2160b38 100644
--- a/y2023/control_loops/superstructure/arm/arm.h
+++ b/y2023/control_loops/superstructure/arm/arm.h
@@ -15,10 +15,7 @@
 
 using frc971::control_loops::arm::EKF;
 
-namespace y2023 {
-namespace control_loops {
-namespace superstructure {
-namespace arm {
+namespace y2023::control_loops::superstructure::arm {
 
 class Arm {
  public:
@@ -116,9 +113,6 @@
   EIGEN_MAKE_ALIGNED_OPERATOR_NEW;
 };
 
-}  // namespace arm
-}  // namespace superstructure
-}  // namespace control_loops
-}  // namespace y2023
+}  // namespace y2023::control_loops::superstructure::arm
 
 #endif  // Y2023_CONTROL_LOOPS_SUPERSTRUCTURE_ARM_ARM_H_