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/y2019/constants.h b/y2019/constants.h
index a36e4b3..0555d4e 100644
--- a/y2019/constants.h
+++ b/y2019/constants.h
@@ -17,8 +17,7 @@
 #include "y2019/control_loops/superstructure/stilts/stilts_plant.h"
 #include "y2019/control_loops/superstructure/wrist/wrist_plant.h"
 
-namespace y2019 {
-namespace constants {
+namespace y2019::constants {
 
 // Has all of our "constants", except the ones that come from other places. The
 // ones which change between robots are put together with a workable way to
@@ -215,7 +214,6 @@
 // them.
 const Values &GetValuesForTeam(uint16_t team_number);
 
-}  // namespace constants
-}  // namespace y2019
+}  // namespace y2019::constants
 
 #endif  // Y2019_CONSTANTS_H_