Removes answerable/non_answerable questions in polls

Now they are either all answerable or non-answerable, so it is not
worth it to make the distinction in code

app/controllers/polls_controller.rb

@@ -9,8 +9,7 @@ class PollsController < ApplicationController
   end
 
   def show
-    @answerable_questions     = @poll.questions.answerable_by(current_user).for_render.sort_for_list
-    @non_answerable_questions = @poll.questions.where.not(id: @answerable_questions.map(&:id)).for_render.sort_for_list
+    @questions     = @poll.questions.for_render.sort_for_list
 
     @answers_by_question_id = {}
     poll_partial_results = Poll::PartialResult.by_question(@poll.question_ids).by_author(current_user.try(:id))