Remove role=treeitem

This was causing an accessability violation, because treeitems must be a child of a tree. https://developer.mozilla.org/en-US/docs/Web/Accessibility/ARIA/Roles/tree_role

Author: jcoyne

app/assets/stylesheets/blacklight/_facets.scss

@@ -126,7 +126,7 @@
     align-items: flex-start;
     padding: 3px 0;
 
-    &[role="treeitem"] {
+    &.treeitem {
       display: block;
     }
 

app/components/blacklight/facet_item_pivot_component.rb

@@ -32,7 +32,7 @@ def call
 
       id = "h-#{self.class.mint_id}" if @collapsing && has_items?
 
-      content_tag @wrapping_element, role: 'treeitem', class: 'treeitem' do
+      content_tag @wrapping_element, class: 'treeitem' do
         concat(content_tag('span', class: "d-flex flex-row align-items-center") do
           concat facet_toggle_button(id) if has_items? && @collapsing
           concat content_tag('span', render(facet), class: "facet-values d-flex flex-row flex-grow-1 #{'facet-leaf-node' if has_items? && @collapsing}", id: id && "#{id}_label")