Fix broken QUnit test for EditorApi

Test introduced in c744bab4 did not stub EditorApi.prototype.get so it
would make a request and pass only on wikis where MediaWiki:Test.css
page was present.

Moved the test to the main QUnit module for EditorApi, no need for
separate module.

Change-Id: I6a637f45ea92deaf89f25814d95d9cd789149a66
Merge "Fix broken QUnit test for EditorApi"