[scroll-animations-1] Editorial: Update confusing use cases intro text

Author: birtles

scroll-animations-1/Overview.bs

@@ -99,7 +99,7 @@ list of use cases</a>.
 
 ## Scrollable picture-story show ## {#scrollable-animation-usecase}
 
-Another pattern is an animation that tells a story where the user
+It is sometimes desired to use an animation to tell a story where the user
 controls the progress of the animation by scrolling or some other
 gesture. This may be because the animation contains a lot of textual
 information which the user may wish to peruse more slowly, it may be for