[css-cascade-5] Remove links to closed issues, resolved no-change

Author: mirisuzanne

css-cascade-5/Overview.bs

@@ -1145,8 +1145,6 @@ Declaring Cascade Layers: the ''@layer'' rule</h4>
 	so the ordering of layers in the light DOM has no impact
 	on the order of identically-named layers in the shadow DOM.
 
-	Issue(w3c/csswg-drafts#5854): Provide a syntax for re-using cascade layers across encapsulation context?
-
 	The ''@layer'' rule can also be used to define new layers
 	without assigning any style rules, by providing only a [=layer name=]:
 
@@ -1355,8 +1353,6 @@ Un-Named Layers</h5>
 		</pre>
 	</div>
 
-	Issue(w3c/csswg-drafts#5792): Should unnamed cascade layers be allowed?
-
 <h3 id="preshint">
 Precedence of Non-CSS Presentational Hints</h3>