[css-overflow-3] Define scroll-behavior with animation type (w3c#8421)

Author: cdoublev

css-overflow-3/Overview.bs

@@ -677,7 +677,7 @@ Smooth Scrolling: the 'scroll-behavior' Property</h3>
 	Applies to: [=scroll containers=]
 	Inherited: no
 	Computed value:    specified value
-	Animatable: no
+	Animatation Type: not animatable
 	Canonical Order: per grammar
 	</pre>