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/testing/path.h b/aos/testing/path.h
index 7f4187d..ebe63fe 100644
--- a/aos/testing/path.h
+++ b/aos/testing/path.h
@@ -4,13 +4,11 @@
 #include <string>
 #include <string_view>
 
-namespace aos {
-namespace testing {
+namespace aos::testing {
 
 // Returns the path to the provided artifact which works
 std::string ArtifactPath(std::string_view path);
 
-}  // namespace testing
-}  // namespace aos
+}  // namespace aos::testing
 
 #endif  // AOS_TESTING_PATH_H_