AO3-6566 ARIA controls must contain the exact ID (#4590)

The ID of the modal controlled by the link to modal is `modal`. The hash
sign must not be included in the reference to the element.

As per Sarken's comment, I've removed the redundant setting of the aria
attribute in HTML options, since it's always overwritten by the
JavaScript.

app/helpers/application_helper.rb

@@ -150,7 +150,7 @@ def link_to_modal(content = "", options = {})
     options[:for] ||= ""
     options[:title] ||= options[:for]
 
-    html_options = { "class" => options[:class] + " modal", "title" => options[:title], "aria-controls" => "#modal" }
+    html_options = { class: "#{options[:class]} modal", title: options[:title] }
     link_to content, options[:for], html_options
   end
 

public/javascripts/ao3modal.js

@@ -193,7 +193,7 @@ jQuery(document).ready(function() {
                         .append(img);
 
                 a.addClass('modal modal-attached')
-                    .attr('aria-controls', '#modal')
+                    .attr('aria-controls', 'modal')
                     .filter(function() {
                         return $(this).closest('.userstuff').length === 0;
                     }).click(function(event){