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/y2019/vision/target_finder.h b/y2019/vision/target_finder.h
index fdcfbde..20bf87a 100644
--- a/y2019/vision/target_finder.h
+++ b/y2019/vision/target_finder.h
@@ -16,8 +16,7 @@
 class Context;
 
 }  // namespace ceres
-namespace y2019 {
-namespace vision {
+namespace y2019::vision {
 
 using aos::vision::BlobList;
 using aos::vision::ContourNode;
@@ -115,7 +114,6 @@
   int current_exposure_ = 0;
 };
 
-}  // namespace vision
-}  // namespace y2019
+}  // namespace y2019::vision
 
 #endif