[css-animations] Drop issue about specifying dynamic changes of animation-name

This has been addressed in changeset
cd78f11

Author: birtles

css-animations/Overview.bs

@@ -1212,8 +1212,6 @@ Acknowledgements</h2>
 
 <p class="issue">Need to <a href="https://lists.w3.org/Archives/Public/www-style/2015Jul/0391.html">specify how keyframes interact</a>.</p>
 
-<p class="issue">Need to specify better handling of dynamic changes of animation-name; see <a href="https://twitter.com/estellevw/status/617525016104583168">conversation</a>.</p>
-
 <h2 id="wg-resolutions-pending">
 Working Group Resolutions that are pending editing</h2>