ovn-sb.xml: Remove IPv4-only restriction from Service Monitors.

The documentation for Service_Monitors in the southbound database state
that only IPv4 is supported. However, IPv6 service monitors have been
supported since OVN 23.03 was released.

This patch addresses the problem by removing the incorrect
documentation.

Fixes: 40a686e ("Add IPv6 support for lb health-check")
Signed-off-by: Mark Michelson <mmichels@redhat.com>
Acked-by: Ales Musil <amusil@redhat.com>
Signed-off-by: Dumitru Ceara <dceara@redhat.com>
(cherry picked from commit 4804d71)

ovn-sb.xml

@@ -4779,8 +4779,7 @@ tcp.flags = RST;
       Each row in this table configures monitoring a service for its liveness.
       The service can be an IPv4 TCP or UDP
       service. <code>ovn-controller</code> periodically sends out service
-      monitor packets and updates the status of the service. Service monitoring
-      for IPv6 services is not supported.
+      monitor packets and updates the status of the service.
     </p>
 
     <p>
@@ -4817,7 +4816,7 @@ tcp.flags = RST;
       </column>
 
       <column name="src_ip">
-        Source IPv4 address to use in the service monitor packet.
+        Source IPv4 or IPv6 address to use in the service monitor packet.
       </column>
 
       <column name="chassis_name">