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/blob/transpose.cc b/aos/vision/blob/transpose.cc
index fe4d4a9..b59e8c5 100644
--- a/aos/vision/blob/transpose.cc
+++ b/aos/vision/blob/transpose.cc
@@ -3,8 +3,7 @@
 #include <algorithm>
 #include <limits>
 
-namespace aos {
-namespace vision {
+namespace aos::vision {
 
 RangeImage Transpose(const RangeImage &img) {
   enum EventT {
@@ -87,5 +86,4 @@
   return RangeImage(min_y, std::move(rows));
 }
 
-}  // namespace vision
-}  // namespace aos
+}  // namespace aos::vision