Deleted an anchor of top of line. Defined "config", but it was reffered from...

Deleted an anchor of top of line. Defined "config", but it was reffered from no where. So, keep code simple.
Signed-off-by: Hirohisa Kawase <hiro.soft@gmail.com>

laravel/documentation/session/config.md

-<a name="config"></a>
 # Session Configuration
 
 ## Contents