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/y2019/jevois/camera/image_stream.cc b/y2019/jevois/camera/image_stream.cc
index 44fd8e5..3268a67 100644
--- a/y2019/jevois/camera/image_stream.cc
+++ b/y2019/jevois/camera/image_stream.cc
@@ -2,8 +2,7 @@
 
 #include "aos/logging/logging.h"
 
-namespace y2019 {
-namespace camera {
+namespace y2019::camera {
 
 void ImageStreamEvent::ProcessHelper(
     aos::vision::DataRef data, aos::monotonic_clock::time_point timestamp) {
@@ -14,5 +13,4 @@
   ProcessImage(data, timestamp);
 }
 
-}  // namespace camera
-}  // namespace y2019
+}  // namespace y2019::camera