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/frc971/input/joystick_input.cc b/frc971/input/joystick_input.cc
index d0d9bc0..19eaa37 100644
--- a/frc971/input/joystick_input.cc
+++ b/frc971/input/joystick_input.cc
@@ -6,8 +6,7 @@
 #include "aos/logging/logging.h"
 #include "frc971/input/robot_state_generated.h"
 
-namespace frc971 {
-namespace input {
+namespace frc971::input {
 
 void JoystickInput::HandleData(const ::aos::JoystickState *joystick_state) {
   data_.Update(joystick_state);
@@ -60,5 +59,4 @@
   RunIteration(data_);
 }
 
-}  // namespace input
-}  // namespace frc971
+}  // namespace frc971::input