import: Use "credentials mode" instead of "omit credentials mode"

There is no longer "omit credentials mode" in the Fetch standard.
The "credentials mode" should be used there.

Suggested by Boris Zbarsky at [1].

[1] http://lists.w3.org/Archives/Public/public-webapps/2014JulSep/0086.html

spec/imports/index.html

@@ -374,7 +374,7 @@ <h3 id="fetching-import">Fetching Import</h3>
     <li><ol>
       <li>Let <var>IMPORT</var> be the <a href="#dfn-imported-document">imported document</a> for <var>LOCATION</var> and <strong>stop</strong>.</li>
     </ol></li>
-    <li><a href="http://fetch.spec.whatwg.org/#concept-fetch">Fetch a resource</a> from <var>LOCATION</var> with <a href="http://fetch.spec.whatwg.org/#concept-request-origin">request's origin</a> set to the <a href="http://www.whatwg.org/specs/web-apps/current-work/multipage/origin-0.html#origin">origin</a> of the <a href="#dfn-master-document">master document</a>, the <a href="http://fetch.spec.whatwg.org/#concept-request-mode">mode</a> to <i>CORS</i> and the <a href="http://fetch.spec.whatwg.org/#concept-request-omit-credentials-mode">omit credentials mode</a> to <i>CORS</i>.</li>
+    <li><a href="http://fetch.spec.whatwg.org/#concept-fetch">Fetch a resource</a> from <var>LOCATION</var> with <a href="http://fetch.spec.whatwg.org/#concept-request-origin">request's origin</a> set to the <a href="http://www.whatwg.org/specs/web-apps/current-work/multipage/origin-0.html#origin">origin</a> of the <a href="#dfn-master-document">master document</a>, the <a href="http://fetch.spec.whatwg.org/#concept-request-mode">mode</a> to <i>CORS</i> and the <a href="http://fetch.spec.whatwg.org/#concept-request-credentials-mode">credentials mode</a> to <i>same-origin</i>.</li>
     <ol>
         <li>If fetched <a href="http://fetch.spec.whatwg.org/#concept-response-type">response type</a> is <i>error</i>:</li>
         <li><ul>