docs($q): mention ES2015 (as a "synonym" for ES6) and remove "harmony"

Closes #14294

Author: stevemao

src/ng/q.js

@@ -13,15 +13,15 @@
  * [Kris Kowal's Q](https://github.com/kriskowal/q).
  *
  * $q can be used in two fashions --- one which is more similar to Kris Kowal's Q or jQuery's Deferred
- * implementations, and the other which resembles ES6 promises to some degree.
+ * implementations, and the other which resembles ES6 (ES2015) promises to some degree.
  *
  * # $q constructor
  *
  * The streamlined ES6 style promise is essentially just using $q as a constructor which takes a `resolver`
- * function as the first argument. This is similar to the native Promise implementation from ES6 Harmony,
+ * function as the first argument. This is similar to the native Promise implementation from ES6,
  * see [MDN](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Promise).
  *
- * While the constructor-style use is supported, not all of the supporting methods from ES6 Harmony promises are
+ * While the constructor-style use is supported, not all of the supporting methods from ES6 promises are
  * available yet.
  *
  * It can be used like so: