Fix logo download link; reported by mausmalone on IRC

git-svn-id: https://svn.xiph.org/websites/theora.org@16892 0101bb08-14d6-0310-b084-bc0e0c8e3800

downloads/index.shtml.en

@@ -54,7 +54,7 @@ and
 
 <h2><a name="media">Marks and media</a></h2>
 <ul>
-  <li><a href="images/logos/theorafish.svg">SVG Theora Fish Logo</a></li>
+  <li><a href="/images/logos/theorafish.svg">SVG Theora Fish Logo</a></li>
 </ul>
 
 <!--#include virtual="/ssi/pagebottom.include" -->