[scroll-animations-1] Editorial: that's → that is

Author: birtles

scroll-animations-1/Overview.bs

@@ -67,7 +67,7 @@ provided it behaves as if the underlying programming interfaces were in place.
 
 ## Relationship to asynchronous scrolling ## {#async-scrolling}
 
-Some user agents support scrolling that's asynchronous with respect to layout
+Some user agents support scrolling that is asynchronous with respect to layout
 or script. This specification is intended to be compatible with such an
 architecture.