Update title of id=use-case-custom-map

Author: Malvoz

index.html

@@ -1490,7 +1490,7 @@ <h5>Required capabilities</h5>
 </section>
 
 <section id="use-case-custom-map" data-ucr-role="use-case">
-<h4>Display custom imagery as a map layer</h4>
+<h4>Display map coverages or other custom tile data</h4>
 <p>
 Many mapping applications require custom imagery
 that goes beyond annotations of an existing map.