Allow to delete answers if the poll has not started yet

Deleting answers was not even possible. But it was possible to delete
questions. So we implemented the same behavior.

app/controllers/admin/poll/questions/answers_controller.rb

@@ -30,6 +30,11 @@ class Admin::Poll::Questions::AnswersController < Admin::Poll::BaseController
     end
   end
 
+  def destroy
+    @answer.destroy!
+    redirect_to admin_question_path(@question), notice: t("admin.answers.destroy.success_notice")
+  end
+
   def order_answers
     ::Poll::Question::Answer.order_answers(params[:ordered_list])
     head :ok