selftests: mptcp: sockopt: drop mptcp_connect var

Global var mptcp_connect defined at the front of mptcp_sockopt.sh is
duplicate with local var mptcp_connect defined in do_transfer(), drop
this useless global one.

Reviewed-by: Matthieu Baerts <matttbe@kernel.org>
Signed-off-by: Geliang Tang <geliang.tang@suse.com>
Signed-off-by: Mat Martineau <martineau@kernel.org>
Link: https://lore.kernel.org/r/20231025-send-net-next-20231025-v1-9-db8f25f798eb@kernel.org


Signed-off-by: Jakub Kicinski <kuba@kernel.org>