abcbus.html: fix URL

esp32/www/abcbus.html

@@ -42,7 +42,7 @@
 	  <input type="text" class="port" name="abc.netserv.port" placeholder="4680" />
 	</label>
 	<p class="help">The network server software is integrated
-	  with <a href="https://www.abc80.org/pub/abc80/abc80sim/">abc80sim</a>
+	  with <a href="https://www.abc80.org/pub/abc80sim/">abc80sim</a>
 	  version 3.7.0 or later.</p>
       </fieldset>
       <button class="submit" type="submit" disabled>Update configuration</button>