selftests/bpf: test_progs/sockopt_sk: Remove version

As pointed by Andrii Nakryiko, _version is useless now, remove it.

Signed-off-by: Yauheni Kaliuta <yauheni.kaliuta@redhat.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20210408061310.95877-1-yauheni.kaliuta@redhat.com