Fix nginx configuration example

Thanks Robby (via IRC)

content-sample/index.md

@@ -284,13 +284,13 @@ still shows no rewritten URLs, force URL rewriting by setting
 `$config['rewrite_url'] = true;` in your `config/config.php`.
 
 If you're using Nginx, you can use the following configuration to enable
-URL rewriting. Don't forget to adjust the path (`/pico/`; line `1` and `4`)
+URL rewriting. Don't forget to adjust the path (`/pico`; line `1` and `4`)
 to match your installation directory. You can then enable URL rewriting by
 setting `$config['rewrite_url'] = true;` in your `config/config.php`.
 
-    location /pico/ {
+    location ~ ^/pico(.*) {
         index index.php;
-        try_files $uri $uri/ /pico/?$uri&$args;
+        try_files $uri $uri/ /pico/?$1&$args;
     }
 
 ## Documentation