it will just disappear after you clic on it, but it will appear to every user that has not  clic on it

You could add this qweb client extension for hide that from rendering

<?xml version="1.0" encoding="UTF-8"?>
<templates xml:space="preserve">
  <t t-name="mail.client_action">
    <div class="o_mail_chat">
     <div class="o_mail_chat_sidebar"/>
     <div class="o_mail_chat_content">
       <t t-if="widget.notification_bar">
         <div class="o_mail_annoying_notification_bar" style="display:none;">
           <span class="o_mail_request_permission">Odoo needs your permission to <a href="#"> enable desktop notifications</a>.</span>
           <span class="fa fa-close"></span>
         </div>
       </t>
     </div>
    </div>
  </t>
</templates>

Add that as a file on your __openerp__.py qweb part