Remove unused NotesController#pass_html_id.

Dead code as far as I can tell. According to `git log -p -G "X-Html-Id"`
was added in 2011 and never used. HTML id is passed to javascript in the
JSON response to `POST /notes.json` instead.

app/controllers/notes_controller.rb

@@ -1,7 +1,6 @@
 class NotesController < ApplicationController
   respond_to :html, :xml, :json, :js
   before_filter :member_only, :except => [:index, :show]
-  before_filter :pass_html_id, :only => [:create]
 
   def search
   end
@@ -68,12 +67,6 @@ private
     params.require(:note).permit(:x, :y, :width, :height, :body, :post_id, :html_id)
   end
 
-  def pass_html_id
-    if params[:note] && params[:note][:html_id]
-      response.headers["X-Html-Id"] = params[:note][:html_id]
-    end
-  end
-
   def index_by_post
     @post_set = PostSets::Note.new(params)
     @posts = @post_set.posts