Remove unused patch file.

It looks like this was included accidentally.

doc/footer.html.patch

---- footer.orig.html	2012-06-11 00:32:00.237427961 -0400
-+++ footer.html	2012-06-11 00:45:51.518437796 -0400
-@@ -6,11 +6,15 @@
-  </div>
- <!--END GENERATE_TREEVIEW-->
- <!--BEGIN !GENERATE_TREEVIEW-->
--<hr class="footer"/><address class="footer"><small>
--$generatedby &#160;<a href="http://www.doxygen.org/index.html">
--<img class="footer" src="$relpath$doxygen.png" alt="doxygen"/>
-+<hr class="footer"/>
-+<table width="100%"><tbody><tr><td>
-+For more information visit the <a href="http://opus-codec.org">Opus Website</a>.
-+</td><td><address class="footer"><small>
-+&copy;$year<br/>
-+$generatedby <a href="http://www.doxygen.org/index.html">
-+<!--<img class="footer" src="$relpath$doxygen.png" alt="doxygen"/>-->doxygen
- </a> $doxygenversion
--</small></address>
-+</small></address></tr></tbody></table>
- <!--END !GENERATE_TREEVIEW-->
- </body>
- </html>