[css-transitions-2] Clarify condition for dispatching transitioncancel

Author: birtles

css-transitions-2/Overview.bs

@@ -281,7 +281,7 @@ after the sample as follows:
       <td><a>interval start</a></td>
     </tr>
     <tr>
-      <td><em>not</em> idle <em>or</em> after &rarr; idle</td>
+      <td><em>not</em> idle and <em>not</em> after &rarr; idle</td>
       <td>{{transitioncancel}}</td>
       <td>The <a>active time</a> of the animation at the moment it was cancelled
           calculated using a <a>fill mode</a> of both.</td>