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/camera_reader.cc b/y2023/vision/camera_reader.cc
index d5f39a0..abffac0 100644
--- a/y2023/vision/camera_reader.cc
+++ b/y2023/vision/camera_reader.cc
@@ -22,8 +22,7 @@
 DEFINE_bool(send_downsized_images, false,
             "Whether to send downsized image for driver cam streaming.");
 
-namespace y2023 {
-namespace vision {
+namespace y2023::vision {
 namespace {
 
 using namespace frc971::vision;
@@ -202,8 +201,7 @@
 }
 
 }  // namespace
-}  // namespace vision
-}  // namespace y2023
+}  // namespace y2023::vision
 
 int main(int argc, char **argv) {
   aos::InitGoogle(&argc, &argv);