dns: remove dns.promises experimental warning

PR-URL: #26592
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Matteo Collina <matteo.collina@gmail.com>
Reviewed-By: Michaël Zasso <targos@protonmail.com>

Author: cjihrig

lib/dns.js

@@ -318,8 +318,6 @@ Object.defineProperties(module.exports, {
       if (promises === null) {
         promises = require('internal/dns/promises');
         promises.setServers = defaultResolverSetServers;
-        process.emitWarning('The dns.promises API is experimental',
-                            'ExperimentalWarning');
       }
       return promises;
     }