Added warning to user for Internet Explorer

As Internet Explorer is not a supported browser anymore, browser Kerberos
configuration page shows warning to user about the same.

Fixes : https://fedorahosted.org/freeipa/ticket/5656

Signed-off-by: Abhijeet Kasurde <akasurde@redhat.com>
Reviewed-By: Pavel Vomacka <pvomacka@redhat.com>
Reviewed-By: Rob Crittenden <rcritten@redhat.com>

install/html/ssbrowser.html

@@ -122,6 +122,7 @@
         </ol>
 
         <h2>Internet Explorer</h2>
+        <p><strong>WARNING:</strong> Internet Explorer is no longer a supported browser.</p>
         <p>
             Once you are able to log into the workstation with your kerberos key you are now able to use that ticket in Internet Explorer.
         </p>