The tests for the comment dialog were failing in Firefox due to a missed spy. The problem is that the text editor was calling `.focus()` on the jQuery-wrapped element when using plain text editors, but the spy was looking for the element itself. This change updates the `TextAreaWrapper` to call `.el.focus()` instead of `.$el.focus()`. This makes things consistent between plain text areas and codemirror versions, so the spy works in both cases. Testing Done: Ran unit tests.