Don't show registration button

doc/EN/usage.org

@@ -574,6 +574,7 @@ Select *Exit to the comand line*.
 #+begin_src bash :tangle no
 sudo su
 sed -i "s|DISABLE_REGISTRATION =.*|DISABLE_REGISTRATION = true|g" /home/gogs/custom/conf/app.ini
+sed -i "s|SHOW_REGISTRATION_BUTTON =.*|SHOW_REGISTRATION_BUTTON = false|g" /home/gogs/custom/conf/app.ini
 systemctl restart gogs
 exit; exit
 #+end_src