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/y2020/control_loops/superstructure/shooter/shooter.cc b/y2020/control_loops/superstructure/shooter/shooter.cc
index c400e34..2792205 100644
--- a/y2020/control_loops/superstructure/shooter/shooter.cc
+++ b/y2020/control_loops/superstructure/shooter/shooter.cc
@@ -9,10 +9,7 @@
 #include "y2020/control_loops/superstructure/finisher/finisher_plant.h"
 #include "y2020/control_loops/superstructure/finisher/integral_finisher_plant.h"
 
-namespace y2020 {
-namespace control_loops {
-namespace superstructure {
-namespace shooter {
+namespace y2020::control_loops::superstructure::shooter {
 
 Shooter::Shooter()
     : finisher_(
@@ -141,7 +138,4 @@
   return status_builder.Finish();
 }
 
-}  // namespace shooter
-}  // namespace superstructure
-}  // namespace control_loops
-}  // namespace y2020
+}  // namespace y2020::control_loops::superstructure::shooter