Reverted access to "actions" for integrations

refs #9865

- see dbd3832967
- we are not aware of any use cases so far
- reverting

core/server/web/api/v2/admin/middleware.js

@@ -20,7 +20,6 @@ const notImplemented = function (req, res, next) {
         themes: ['POST'],
         subscribers: ['GET', 'PUT', 'DELETE', 'POST'],
         configuration: ['GET'],
-        actions: ['GET'],
         webhooks: ['POST', 'DELETE']
     };