Remove one more use of responsible document (#243)

Author: jgraham

index.bs

@@ -3822,7 +3822,8 @@ To <dfn>get the realm info</dfn> given |environment settings|:
   <dl>
     <dt>|global object| is a [=Window=] object
     <dd>
-      1. Let |document| be |environment settings|' [=responsible document=].
+      1. Let |document| be |environment settings|' [=relevant global object=]'s
+         <a>associated <code>Document</code></a>.
       1. Let |browsing context| be |document|'s [=/browsing context=].
       1. Let |context id| be the [=browsing context id=] for |browsing context|.
       1. Let |realm info| be a map matching the <code>WindowRealmInfo</code> production,