weston.ini: Move binding-modifier to shell section.

The variable has no effect as part of the screensaver section.

weston.ini

@@ -5,6 +5,7 @@ background-color=0xff002244
 panel-color=0x90ff0000
 locking=true
 animation=zoom
+#binding-modifier=ctrl
 
 #type=tablet-shell.so
 #lockscreen-icon=/usr/share/icons/gnome/256x256/actions/lock.png
@@ -31,4 +32,3 @@ path=./clients/flower
 # Uncomment path to disable screensaver
 path=/usr/libexec/weston-screensaver
 duration=600
-#binding-modifier=ctrl