Update web_server_configuration.rst

I had problems using ProxyPassMatch and mod_rewrite and now I use SetHandler to send the request to proxy. This change works fine and should be the standar configuration in the future for Apache and php-fpm.
You can read the php developers discussion here http://www.serverphorums.com/read.php?7,956732 or some about problems fixed here http://blog.famillecollet.com/post/2014/03/28/PHP-FPM-and-HTTPD-2.4-improvement