Clarify the OWNERS file

Test: gerrit
Change-Id: I9f3914600a84ff2dc11ec0064e1f39f18aaace1d
diff --git a/OWNERS b/OWNERS
index 9594320..1944029 100644
--- a/OWNERS
+++ b/OWNERS
@@ -1,8 +1,11 @@
+# Current team members
 adelva@google.com
-ghartman@google.com
 jemoreira@google.com
 malchev@google.com
 muntsinger@google.com
 natsu@google.com
 rammuthiah@google.com
 schuffelen@google.com
+
+# Former team members
+ghartman@google.com