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/timestamp_channel.cc b/aos/network/timestamp_channel.cc
index 52032f5..778c2e7 100644
--- a/aos/network/timestamp_channel.cc
+++ b/aos/network/timestamp_channel.cc
@@ -10,8 +10,7 @@
             "channels are configured to have at least as great a frequency as "
             "the corresponding data channel.");
 
-namespace aos {
-namespace message_bridge {
+namespace aos::message_bridge {
 
 ChannelTimestampFinder::ChannelTimestampFinder(
     const Configuration *configuration, const std::string_view name,
@@ -143,5 +142,4 @@
   return result.first->second.get();
 }
 
-}  // namespace message_bridge
-}  // namespace aos
+}  // namespace aos::message_bridge