dns: fix test-net-dns-lookup.js

PR-URL: #39987
Fixes: #31566
Refs: #6307
Refs: #20710
Refs: #38099
Reviewed-By: Antoine du Hamel <duhamelantoine1995@gmail.com>
Reviewed-By: Matteo Collina <matteo.collina@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Michael Dawson <midawson@redhat.com>

test/parallel/test-net-dns-lookup.js

@@ -34,7 +34,7 @@ server.listen(0, common.mustCall(function() {
     .on('lookup', common.mustCall(function(err, ip, type, host) {
       assert.strictEqual(err, null);
       assert.match(ip, /^(127\.0\.0\.1|::1)$/);
-      assert.match(type.toString, /^(4|6)$/);
+      assert.match(type.toString(), /^(4|6)$/);
       assert.strictEqual(host, 'localhost');
     }));
 }));