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/ipc_lib/event_test.cc b/aos/ipc_lib/event_test.cc
index 40c48b2..eda9156 100644
--- a/aos/ipc_lib/event_test.cc
+++ b/aos/ipc_lib/event_test.cc
@@ -8,8 +8,7 @@
 #include "aos/testing/test_logging.h"
 #include "aos/time/time.h"
 
-namespace aos {
-namespace testing {
+namespace aos::testing {
 
 namespace chrono = ::std::chrono;
 namespace this_thread = ::std::this_thread;
@@ -89,5 +88,4 @@
   EXPECT_GE(finish_time - start_time, kWaitTime);
 }
 
-}  // namespace testing
-}  // namespace aos
+}  // namespace aos::testing