[Spec] Fix broken reference to permissions-policy (#1007)

Author: stephenmcgruer

index.html

@@ -2303,8 +2303,8 @@ <h2>
       <p>
         This specification defines a [=policy-controlled feature=] identified
         by the string <dfn class="permission">"payment"</dfn>
-        [[permissions-policy]]. Its <a>default allowlist</a> is
-        '<code>self</code>'.
+        [[permissions-policy]]. Its [=policy-controlled feature/default
+        allowlist=] is '<code>self</code>'.
       </p>
       <aside class="note">
         <p>