Adjust test fixture

Jay, I had a test for this 😄

Author: ralfhandl

tests/md2html/fixtures/basic-new.html

@@ -24,7 +24,7 @@
 </code></pre>
 <pre class="nohighlight" tabindex="0"><code>text/plain
 </code></pre>
-<pre class="highlight " tabindex="0"><code>no language
+<pre class="nohighlight" tabindex="0"><code>no language
 </code></pre>
 </section></section><section class="appendix"><h1>Appendix A: Revision History</h1>
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