Nest some more namespaces

Did someone previously suggest that all namespace had been
nested?  Silly.

Signed-off-by: Stephan Pleines <pleines.stephan@gmail.com>
Change-Id: I22278c1caaeba8b47dc46fb2ed3078c20a11e190
diff --git a/aos/vision/math/segment.h b/aos/vision/math/segment.h
index d6927cb..8ae91e3 100644
--- a/aos/vision/math/segment.h
+++ b/aos/vision/math/segment.h
@@ -5,8 +5,7 @@
 
 #include "aos/vision/math/vector.h"
 
-namespace aos {
-namespace vision {
+namespace aos::vision {
 
 template <int Size>
 class Segment {
@@ -76,7 +75,6 @@
   Vector<Size> B_;
 };
 
-}  // namespace vision
-}  // namespace aos
+}  // namespace aos::vision
 
 #endif  // AOS_VISION_COMP_GEO_VECTOR_H_