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/vision/charuco_lib.cc b/frc971/vision/charuco_lib.cc
index 8e8acc3..c24d02c 100644
--- a/frc971/vision/charuco_lib.cc
+++ b/frc971/vision/charuco_lib.cc
@@ -38,8 +38,7 @@
 
 DECLARE_bool(enable_ftrace);
 
-namespace frc971 {
-namespace vision {
+namespace frc971::vision {
 namespace chrono = std::chrono;
 using aos::monotonic_clock;
 
@@ -600,5 +599,4 @@
   return os;
 }
 
-}  // namespace vision
-}  // namespace frc971
+}  // namespace frc971::vision