remove es6-promise polyfill
|Assigned To:||Tomer Brisker|
|Target version:||Team Daniel - Iteration 9|
|Found in release:||Pull request:||https://github.com/theforeman/foreman/pull/4164|
|Velocity based estimate||-|
polyfill was added because promises are not supported on node 0.10. Now that our builders have been upgraded to newer versions this polyfill can be removed.