libmsc: Remove comment not applying anymore

The change-id I7276d356d805a83ebeec72b02c8563b7135ea0b6 added msg_ref to
the databse but forgot to remove the comment stating it's not being
stored.

Change-Id: I204f098c8f2a480405446113e2181b2c53700cf3
diff --git a/src/libmsc/db.c b/src/libmsc/db.c
index 78e022d..3495806 100644
--- a/src/libmsc/db.c
+++ b/src/libmsc/db.c
@@ -750,7 +750,6 @@
 	sms->protocol_id = dbi_result_get_ulonglong(result, "protocol_id");
 	sms->data_coding_scheme = dbi_result_get_ulonglong(result,
 						  "data_coding_scheme");
-	/* sms->msg_ref is temporary and not stored in DB */
 
 	sms->dst.npi = dbi_result_get_ulonglong(result, "dest_npi");
 	sms->dst.ton = dbi_result_get_ulonglong(result, "dest_ton");