Nest all namespaces

The compiler supports this now.  We can type less going forward.
No functional changes.

Signed-off-by: Stephan Pleines <pleines.stephan@gmail.com>
Change-Id: I29d6fa4f9aacc0e381f1a7637294db0392466995
diff --git a/aos/json_to_flatbuffer_test.cc b/aos/json_to_flatbuffer_test.cc
index 4900711..85e21d4 100644
--- a/aos/json_to_flatbuffer_test.cc
+++ b/aos/json_to_flatbuffer_test.cc
@@ -7,8 +7,7 @@
 #include "aos/json_to_flatbuffer_generated.h"
 #include "aos/testing/path.h"
 
-namespace aos {
-namespace testing {
+namespace aos::testing {
 
 class JsonToFlatbufferTest : public ::testing::Test {
  public:
@@ -402,5 +401,4 @@
           ArtifactPath("aos/json_to_flatbuffer_test_spaces.json"))));
 }
 
-}  // namespace testing
-}  // namespace aos
+}  // namespace aos::testing