test: fix comment about DNS lookup test

PR-URL: #35080
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Rich Trott <rtrott@gmail.com>

test/parallel/test-c-ares.js

@@ -42,8 +42,7 @@ const dnsPromises = dns.promises;
   assert.strictEqual(res.family, 6);
 })();
 
-// Try resolution without callback
-
+// Try resolution without hostname.
 dns.lookup(null, common.mustCall((error, result, addressType) => {
   assert.ifError(error);
   assert.strictEqual(result, null);