rename client.conf to client.ovpn

As the name of the file changed here : https://github.com/Chocobozzz/OpenVPN-Admin/pull/2 it should change also here, otherwise we get `sed: impossible de lire ./client-conf/windows/client.conf: Aucun fichier ou dossier de ce type`

install.sh

@@ -209,7 +209,7 @@ sed -i "s/\$pass = '';/\$pass = '$mysql_pass';/" "./include/config.php"
 
 # Replace in the client configurations with the ip of the server
 sed -i "s/remote xxx\.xxx\.xxx\.xxx 443/remote $ip_server 443/" "./client-conf/gnu-linux/client.conf"
-sed -i "s/remote xxx\.xxx\.xxx\.xxx 443/remote $ip_server 443/" "./client-conf/windows/client.conf"
+sed -i "s/remote xxx\.xxx\.xxx\.xxx 443/remote $ip_server 443/" "./client-conf/windows/client.ovpn"
 
 # Copy ta.key inside the client-conf directory
 cp "/etc/openvpn/"{ca.crt,ta.key} "./client-conf/gnu-linux/"