Add berchet@ to owners file

Also clean up old owners.

Change-Id: I7d7c3460faf294b3a9e3f1668653a822f4ff761d
Test: N/A
diff --git a/OWNERS b/OWNERS
index b5714c9..77c4fde 100644
--- a/OWNERS
+++ b/OWNERS
@@ -1,4 +1,4 @@
 arthuri@google.com
 bduddie@google.com
-karthikmb@google.com
+berchet@google.com
 stange@google.com