fix(core): remove extra nl_NL language from constant file (#1155)

Author: antleblanc

packages/manager/modules/core/src/manager-core.constants.js

@@ -20,9 +20,6 @@ export const LANGUAGES = {
   }, {
     name: 'Lietuviškai',
     key: 'lt_LT',
-  }, {
-    name: 'Nederlands',
-    key: 'nl_NL',
   }, {
     name: 'Polski',
     key: 'pl_PL',