Update Overview.bs (#11133)

Fix animmations -> animations typo

css-ui-4/Overview.bs

@@ -1244,7 +1244,7 @@ Animation of the insertion caret: 'caret-animation'</h4>
 	</div>
 
 	<div class=advisement>
-		If a user agent is unwilling to yield control of caret animmations
+		If a user agent is unwilling to yield control of caret animations
 		to page authors and would not honor ''caret-animation: manual'',
 		it must not implement the property at all.