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/events/shm_event_loop_test.cc b/aos/events/shm_event_loop_test.cc
index 2134687..4db0c7d 100644
--- a/aos/events/shm_event_loop_test.cc
+++ b/aos/events/shm_event_loop_test.cc
@@ -10,8 +10,7 @@
 #include "aos/network/team_number.h"
 #include "aos/realtime.h"
 
-namespace aos {
-namespace testing {
+namespace aos::testing {
 namespace {
 namespace chrono = ::std::chrono;
 
@@ -447,5 +446,4 @@
 INSTANTIATE_TEST_SUITE_P(ShmEventLoopPinDeathTest, ShmEventLoopDeathTest,
                          ::testing::Values(ReadMethod::PIN));
 
-}  // namespace testing
-}  // namespace aos
+}  // namespace aos::testing