Implement @iherman's suggested change on retrieving contexts.

Author: gkellogg

index.html

@@ -9096,7 +9096,7 @@ <h3>Graph Containers</h3>
 
   <p>In order to use an external context with an ordinary JSON document,
     when retrieving an ordinary JSON document via HTTP, processors MUST
-    retrieve any <a>JSON-LD document</a> referenced by a
+    attempt to retrieve any <a>JSON-LD document</a> referenced by a
     <a data-cite="RFC8288#section-3">Link Header</a> with:</p>
 
   <ul>