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/vision/camera_reader.cc b/y2020/vision/camera_reader.cc
index a63becd..251f988 100644
--- a/y2020/vision/camera_reader.cc
+++ b/y2020/vision/camera_reader.cc
@@ -23,8 +23,7 @@
 DEFINE_bool(use_prev_pose, true,
             "If true, use previous pose estimate as seed for next estimate.");
 
-namespace frc971 {
-namespace vision {
+namespace frc971::vision {
 
 const sift::CameraCalibration *CameraReader::FindCameraCalibration() const {
   const std::string_view node_name = event_loop_->node()->name()->string_view();
@@ -541,5 +540,4 @@
   return fbb->CreateVector(features_vector);
 }
 
-}  // namespace vision
-}  // namespace frc971
+}  // namespace frc971::vision