knights: disable the animation by default

It is quite personal test but, in fairness, current animations are buggy
and quite distracting, there's people who would prefer such animation
but by default this gives much worse user experience.

src/knights.kcfg

@@ -29,7 +29,7 @@
         <choice name="Slow" />
       </choices>
 	  <label>Moves animation speed</label>
-	  <default>Normal</default>
+	  <default>Instant</default>
     </entry>
     <entry name="animateBoard" type="Bool">
       <label>whether the Board is animated during rotating and resizing</label>