Fix broken Protocol link in top nav.

Author: mugurm

_includes/nav.html

@@ -20,7 +20,7 @@
         <li><a href="/docs/">Documentation</a></li>
         <li><a href="/contribute/">Contribute</a></li>
         <li><a href="/faq/">FAQ</a></li>
-        <li><a href="/docs/reference/protocol-http2.html">Protocol</a></li>
+        <li><a href="/docs/guides/wire.html">Protocol</a></li>
 
         <!-- Hide link to blog until we have actual posts -->
         <!-- <li><a href="/blog/" title="">Blog</a></li> -->