MGCP_Templates: Accept 200 and 250 as ACK for DLCX

Both codes are valid as response to a DLCX, see RFC3661 Ch 2.2:
"""
The 250 response code can be used to acknowledge a successful completion
of a DeleteConnection command.  However, a 200 response code is also
appropriate.
"""
diff --git a/library/MGCP_Templates.ttcn b/library/MGCP_Templates.ttcn
index 6d2a689..3fa7bd1 100644
--- a/library/MGCP_Templates.ttcn
+++ b/library/MGCP_Templates.ttcn
@@ -135,7 +135,7 @@
 
 	template MgcpResponse tr_DLCX_ACK := {
 		line := {
-			code := "200",
+			code := ("200", "250"),
 			trans_id := ?,
 			string := "OK"
 		},