Remove note about --force option on server:start

The --force option is not part of the WebServerBundle, so remove the note about using that option.

Author: mloberg

setup/built_in_web_server.rst

@@ -35,15 +35,6 @@ can change the socket passing an IP address and a port as a command-line argumen
 
     $ php bin/console server:start 192.168.0.1:8080
 
-.. note::
-
-    You can use the ``--force`` option to force the web server start
-    if the process wasn't correctly stopped (without using the ``server:stop`` command).
-
-    .. code-block:: bash
-
-        $ php bin/console server:start --force
-
 .. note::
 
     You can use the ``server:status`` command to check if a web server is