Remove duplicated setupNoteForm method

#### What does this MR do?

This PR removes a duplicated method `setupForm` in `notes.js.coffee`. Originally line [258](https://github.com/gitlabhq/gitlabhq/blob/master/app/assets/javascripts/notes.js.coffee#L258) and line [415](https://github.com/gitlabhq/gitlabhq/blob/master/app/assets/javascripts/notes.js.coffee#L415) define the same method.