[xfce] enable dpms in xfce power manager

overlays/xfce/etc/skel/.config/xfce4/xfconf/xfce-perchannel-xml/xfce4-power-manager.xml

@@ -2,7 +2,7 @@
 
 <channel name="xfce4-power-manager" version="1.0">
   <property name="xfce4-power-manager" type="empty">
-    <property name="dpms-enabled" type="bool" value="false"/>
+    <property name="dpms-enabled" type="bool" value="true"/>
     <property name="blank-on-ac" type="int" value="0"/>
     <property name="lock-screen-suspend-hibernate" type="bool" value="false"/>
     <property name="logind-handle-lid-switch" type="bool" value="false"/>