stun: eliminate a warning.

code to dissect PASSWORD-ALGORITHMS and PASSWORD-ALGORITHM attributes is
ready to go.

Change-Id: I6fcfb1da49c596a11b3c5b0e3dce51e47f1f7c1c
Reviewed-on: https://code.wireshark.org/review/38047
Reviewed-by: Guy Harris <gharris@sonic.net>

epan/dissectors/packet-stun.c

@@ -557,12 +557,14 @@ static const value_string federation_vals[] = {
     {0x00, NULL}
 };
 
+#if 0
 static const value_string password_algorithm_vals[] = {
     {0x0000, "Reserved"},
     {0x0001, "MD5"},
     {0x0002, "SHA-256"},
     {0x0000, NULL}
 };
+#endif
 
 static guint
 get_stun_message_len(packet_info *pinfo _U_, tvbuff_t *tvb,