Remove unused JavaScript poll token code

We don't load the token message since commit 585f9ea5, so the JavaScript
to show it wasn't doing anything anymore.

app/assets/javascripts/polls.js.coffee

@@ -19,14 +19,6 @@ App.Polls =
     @token = App.Polls.generateToken()
     App.Polls.replaceToken()
 
-    $(".js-question-answer").on
-      click: =>
-        token_message = $(".js-token-message")
-        if !token_message.is(":visible")
-          token_message.html("#{token_message.html()}<br><strong>#{@token}</strong>")
-          token_message.show()
-    false
-
     $(".zoom-link").on "click", (event) ->
       element = event.target
       answer = $(element).closest("div.answer")

app/assets/stylesheets/participation.scss

@@ -346,12 +346,6 @@
   }
 
   .callout {
-    &.token-message {
-      background-color: #fff;
-      border-color: $info-border;
-      color: $color-info;
-    }
-
     &.proposal-retired {
       font-size: $base-font-size;
     }

spec/features/polls/voter_spec.rb

@@ -177,8 +177,6 @@ describe "Voter" do
 
         visit poll_path(poll)
 
-        expect(page).not_to have_selector(".js-token-message")
-
         expect(page).to have_content "You have already participated in this poll. If you vote again it will be overwritten."
         within("#poll_question_#{question.id}_answers") do
           expect(page).not_to have_link(answer_yes.title)