Nest some more namespaces

Did someone previously suggest that all namespace had been
nested?  Silly.

Signed-off-by: Stephan Pleines <pleines.stephan@gmail.com>
Change-Id: I22278c1caaeba8b47dc46fb2ed3078c20a11e190
diff --git a/aos/util/file.h b/aos/util/file.h
index e825e4c..e0d5c6b 100644
--- a/aos/util/file.h
+++ b/aos/util/file.h
@@ -17,8 +17,7 @@
 
 #include "aos/scoped/scoped_fd.h"
 
-namespace aos {
-namespace util {
+namespace aos::util {
 
 // Returns the complete contents of filename. LOG(FATAL)s if any errors are
 // encountered.
@@ -122,7 +121,6 @@
   aos::ScopedFD file_;
 };
 
-}  // namespace util
-}  // namespace aos
+}  // namespace aos::util
 
 #endif  // AOS_UTIL_FILE_H_