Editorial: Fix ReSpec error with ancestor browsing context (#89)

Author: mustaqahmed

index.html

@@ -206,8 +206,8 @@ <h2>
           <p>
             Pointer lock MUST fail unless the <a>target</a>'s
             <a>shadow-including root</a> is the [=navigable/active document=]
-            of a [=Document/browsing context=] which is (or has an <a>ancestor
-            browsing context</a> which is) in focus by a window which is in
+            of a [=Document/browsing context=] which is (or has an [=tree/ancestor=]
+            [=Document/browsing context=] which is) in focus by a window which is in
             focus by the operating system's window manager. The <a>target</a>
             element and its [=Document/browsing context=] need not be in focus.
           </p>