ART: Add missing namespace comments

Add closing namespace comments.

Bug: 32619234
Test: m
Change-Id: I1f50e09dcd1038c4b540b87e5c19e319c1f592e4
diff --git a/runtime/method_handles.h b/runtime/method_handles.h
index 5bea0ab..e8a2dce 100644
--- a/runtime/method_handles.h
+++ b/runtime/method_handles.h
@@ -29,7 +29,7 @@
 namespace mirror {
   class MethodHandle;
   class MethodType;
-}  // mirror
+}  // namespace mirror
 
 class ShadowFrame;