Merge pull request #20873 from emberjs/delete-unused

Delete unused external-helpers package

Author: ef4

packages/external-helpers/lib/external-helpers.js

@@ -168,7 +168,6 @@ function packages() {
 
       // these packages are special and don't get included here
       'loader/**',
-      'external-helpers/**',
       'ember-template-compiler/**',
       'internal-test-helpers/**',