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/aos/vision/image/jpeg_routines.cc b/aos/vision/image/jpeg_routines.cc
index b41729f..9d46895 100644
--- a/aos/vision/image/jpeg_routines.cc
+++ b/aos/vision/image/jpeg_routines.cc
@@ -14,8 +14,7 @@
 
 #include "aos/logging/logging.h"
 
-namespace aos {
-namespace vision {
+namespace aos::vision {
 
 namespace {
 
@@ -248,5 +247,4 @@
   return true;
 }
 
-}  // namespace vision
-}  // namespace aos
+}  // namespace aos::vision