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/vision/viewer.cc b/y2023/vision/viewer.cc
index e03680c..78731e5 100644
--- a/y2023/vision/viewer.cc
+++ b/y2023/vision/viewer.cc
@@ -18,8 +18,7 @@
 DEFINE_int32(rate, 100, "Time in milliseconds to wait between images");
 DEFINE_double(scale, 1.0, "Scale factor for images being displayed");
 
-namespace y2023 {
-namespace vision {
+namespace y2023::vision {
 namespace {
 
 using frc971::vision::CameraImage;
@@ -108,8 +107,7 @@
 }
 
 }  // namespace
-}  // namespace vision
-}  // namespace y2023
+}  // namespace y2023::vision
 
 int main(int argc, char **argv) {
   aos::InitGoogle(&argc, &argv);