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/actors/auto_splines.h b/y2019/actors/auto_splines.h
index 7b56c11..4d6fbc1 100644
--- a/y2019/actors/auto_splines.h
+++ b/y2019/actors/auto_splines.h
@@ -11,8 +11,7 @@
 
 */
 
-namespace y2019 {
-namespace actors {
+namespace y2019::actors {
 
 class AutonomousSplines {
  public:
@@ -88,7 +87,6 @@
           *builder);
 };
 
-}  // namespace actors
-}  // namespace y2019
+}  // namespace y2019::actors
 
 #endif  // Y2019_ACTORS_AUTO_SPLINES_H_