[selectors-4] Remove issue

Author: fantasai

selectors/Overview.bs

@@ -881,9 +881,6 @@ Pseudo-classing Pseudo-elements</h4>
 	are not valid when compounded to a pseudo-element;
 	so, for example, ''::before:first-child'' is an invalid selector.
 
-	Issue: <a href="https://hg.csswg.org/drafts/diff/8e32bf889326/selectors/Overview.bs">Tab proposes</a>
-	that we use a blacklist approach instead of a whitelist approach here.
-
 <h4 id="pseudo-element-structure">
 Internal Structure</h4>