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/network/message_bridge_test.cc b/aos/network/message_bridge_test.cc
index cc46926..c211c89 100644
--- a/aos/network/message_bridge_test.cc
+++ b/aos/network/message_bridge_test.cc
@@ -16,10 +16,7 @@
 #include "aos/testing/path.h"
 #include "aos/util/file.h"
 
-namespace aos {
-
-namespace message_bridge {
-namespace testing {
+namespace aos::message_bridge::testing {
 
 // Note: All of these tests spin up ShmEventLoop's in separate threads to allow
 // us to run the "real" message bridge. This requires extra threading and timing
@@ -1440,6 +1437,4 @@
               true},
         Param{"message_bridge_test_common_config.json", false}));
 
-}  // namespace testing
-}  // namespace message_bridge
-}  // namespace aos
+}  // namespace aos::message_bridge::testing