Clarify recommendation for restricting new features.

w3c/webcrypto#28 noted that the current recommendations were confusing
as they suggested both throwing and hiding the interface. This patch
clarifies that either/or is completely acceptable.

index.html

@@ -1063,8 +1063,7 @@ <h3 class="heading settled" data-level="7.3" id="new"><span class="secno">7.3. <
        </ol>
      </ol>
     </div>
-    <p>Authors should also ensure that sensitive APIs are only exposed to <a data-link-type="dfn" href="#secure-context" id="ref-for-secure-context-32">secure
-  contexts</a> by guarding them with the <code>[SecureContext]</code> attribute:</p>
+    <p>Authors could alternatively ensure that sensitive APIs are only exposed to <a data-link-type="dfn" href="#secure-context" id="ref-for-secure-context-32">secure contexts</a> by guarding them with the <code>[SecureContext]</code> attribute:</p>
     <div class="example" id="example-63db205d">
      <a class="self-link" href="#example-63db205d"></a> 
 <pre class="idl highlight def">[<span class="nv" idltype="extended-attribute">SecureContext</span>]

index.src.html

@@ -1002,8 +1002,8 @@ <h3 id="new">Restricting New Features</h3>
     </ol>
   </div>
 
-  Authors should also ensure that sensitive APIs are only exposed to <a>secure
-  contexts</a> by guarding them with the `[SecureContext]` attribute:
+  Authors could alternatively ensure that sensitive APIs are only exposed to
+  <a>secure contexts</a> by guarding them with the `[SecureContext]` attribute:
 
   <div class="example">
     <pre class="idl">