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/vector.h b/aos/vision/math/vector.h
index 5e7520f..ce29901 100644
--- a/aos/vision/math/vector.h
+++ b/aos/vision/math/vector.h
@@ -5,8 +5,7 @@
 
 #include "Eigen/Dense"
 
-namespace aos {
-namespace vision {
+namespace aos::vision {
 
 // Represents an n-dimensional vector of doubles with various convenient
 // shortcuts for common operations.
@@ -222,7 +221,6 @@
   return nv;
 }
 
-}  // namespace vision
-}  // namespace aos
+}  // namespace aos::vision
 
 #endif  // AOS_VISION_MATH_VECTOR_H_