gitweb: use {url} as entrypoint in notfound.tmpl instead of /

templates/gitweb/notfound.tmpl

@@ -12,7 +12,7 b''
 The specified repository "{repo|escape}" is unknown, sorry.
 <br/>
 <br/>
-Please go back to the <a href="/">main repository list page</a>.
+Please go back to the <a href="{url}">main repository list page</a>.
 </div>
 
 {footer}