formatdomain.html.in: fix tickpolicy

there is no option "none":

>From libvirt/src/conf/domain_conf.c

<snip>
VIR_ENUM_IMPL(virDomainTimerTickpolicy,
VIR_DOMAIN_TIMER_TICKPOLICY_LAST,
              "delay",
              "catchup",
              "merge",
              "discard");
</snip>

Replacing with delay.
Signed-off-by: NDouglas Schilling Landgraf <dougsland@redhat.com>

docs/formatdomain.html.in

@@ -746,7 +746,7 @@
     <timer name="rtc" tickpolicy="catchup" track="guest">
       <catchup threshold=123 slew=120 limit=10000/>
     </timer>
-    <timer name="pit" tickpolicy="none"/>
+    <timer name="pit" tickpolicy="delay"/>
   </clock>
   ...</pre>