doc: migration-guide: mention change of socket service callback

mention change of callback function for the socket service.

Signed-off-by: Fin Maaß <f.maass@vogl-electronic.com>

doc/releases/migration-guide-4.0.rst

@@ -496,6 +496,10 @@ Networking
 * The ``work_q`` parameter to ``NET_SOCKET_SERVICE_SYNC_DEFINE`` and
   ``NET_SOCKET_SERVICE_SYNC_DEFINE_STATIC`` has been removed as it was always ignored. (:github:`79446`)
 
+* The callback function for the socket service has changed. The
+  ``struct k_work *work`` parameter has been replaced with a pointer to the
+  ``struct net_socket_service_event *pev`` parameter. (:github:`80041`)
+
 * Deprecated the :kconfig:option:`CONFIG_NET_SOCKETS_POLL_MAX` option in favour of
   :kconfig:option:`CONFIG_ZVFS_POLL_MAX`.