block/throttle-groups: fix throttle properties typename

The getter and setter use visit_type_int64, not visit_type_int.

Fixes: 432d889e55 ("block: convert ThrottleGroup to object with QOM")
Reviewed-by: Mark Cave-Ayland <mark.caveayland@nutanix.com>
Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>

block/throttle-groups.c

@@ -984,7 +984,7 @@ static void throttle_group_obj_class_init(ObjectClass *klass,
     for (i = 0; i < sizeof(properties) / sizeof(ThrottleParamInfo); i++) {
         object_class_property_add(klass,
                                   properties[i].name,
-                                  "int",
+                                  "int64",
                                   throttle_group_get,
                                   throttle_group_set,
                                   NULL, &properties[i]);