man: Remove obsolete RHEL 5 krb5.conf note from sssd-ad

This patch removes the RHEL 5 reference from sssd-ad(5) man-page
as it is no longer relevant in supported deployments.

Signed-off-by: Akshay Sakure <asakure@redhat.com>
Reviewed-by: Alexey Tikhonov <atikhono@redhat.com>

Author: asakure

src/man/sssd-ad.5.xml

@@ -1176,11 +1176,6 @@ ad_gpo_map_deny = +my_pam_service
                             the updates, if it is not otherwise specified
                             by using the <quote>dyndns_iface</quote> option.
                         </para>
-                        <para>
-                            NOTE: On older systems (such as RHEL 5), for this
-                            behavior to work reliably, the default Kerberos
-                            realm must be set properly in /etc/krb5.conf
-                        </para>
                         <para>
                             Default: true
                         </para>