Nest all namespaces

The compiler supports this now.  We can type less going forward.
No functional changes.

Signed-off-by: Stephan Pleines <pleines.stephan@gmail.com>
Change-Id: I29d6fa4f9aacc0e381f1a7637294db0392466995
diff --git a/y2023/constants.cc b/y2023/constants.cc
index 6b63cda..0154453 100644
--- a/y2023/constants.cc
+++ b/y2023/constants.cc
@@ -15,8 +15,7 @@
 #include "y2023/control_loops/superstructure/roll/integral_roll_plant.h"
 #include "y2023/control_loops/superstructure/wrist/integral_wrist_plant.h"
 
-namespace y2023 {
-namespace constants {
+namespace y2023::constants {
 
 Values MakeValues(uint16_t team) {
   LOG(INFO) << "creating a Constants for team: " << team;
@@ -179,5 +178,4 @@
 
 Values MakeValues() { return MakeValues(aos::network::GetTeamNumber()); }
 
-}  // namespace constants
-}  // namespace y2023
+}  // namespace y2023::constants