MDL-73584 lib: Remove role menubar from Actions menu

The menubar role defined in the "menubar d-flex" element is not
required and it's causing the following error "Required ARIA children
role not present: group, menuitemradio, menuitem, menuitemcheckbox".

lib/outputcomponents.php

@@ -4237,7 +4237,6 @@ class action_menu implements renderable, templatable {
         $this->attributesprimary = array(
             'id' => 'action-menu-'.$this->instance.'-menubar',
             'class' => 'menubar',
-            'role' => 'menubar'
         );
         $this->attributessecondary = array(
             'id' => 'action-menu-'.$this->instance.'-menu',