Merge pull request #4160 from edx/adam/browser-warning-lte-ie8

only display browser warning for <= IE8 (LMS-2732)

lms/templates/navigation.html

@@ -129,7 +129,7 @@ site_status_msg = get_site_status_msg(course_id)
   </nav>
 </header>
 % if course:
-<!--[if IE]>
+<!--[if lte IE 8]>
 <div class="ie-banner" aria-hidden="true">${_('<strong>Warning:</strong> Your browser is not fully supported. We strongly recommend using {chrome_link_start}Chrome{chrome_link_end} or {ff_link_start}Firefox{ff_link_end}.').format(chrome_link_start='<a href="https://www.google.com/intl/en/chrome/browser/" target="_blank">', chrome_link_end='</a>', ff_link_start='<a href="http://www.mozilla.org/en-US/firefox/new/" target="_blank">', ff_link_end='</a>')}</div>
 <![endif]-->
 % endif