nathelper: small spelling fix in docs

src/modules/nathelper/doc/nathelper_admin.xml

@@ -829,7 +829,7 @@ if(is_rfc1918("$rd")) {
 		</title>
 		<para>
 		Reads <quote>;alias=ip~port~transport</quote> from Contact header then
-		writes to target avp as a sip uri.
+		writes to target pseudo-variable as a sip uri.
 		</para>
 		<para>
 		This function can be used from