BACKPORT: wireguard: selftests: remove old conntrack kconfig value

On recent kernels, this config symbol is no longer used.

Bug: 254441685
Reported-by: Rui Salvaterra <rsalvaterra@gmail.com>
Fixes: e7096c131e51 ("net: WireGuard secure network tunnel")
Cc: stable@vger.kernel.org
Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
(cherry picked from commit acf2492b51c9a3c4dfb947f4d3477a86d315150f)
Signed-off-by: Lee Jones <joneslee@google.com>
Change-Id: I6e1d5e0bf06c65bda448d1dd79aacc91847a22b5