selftests/bpf: sockmap_listen cleanup: Drop af_unix redir tests

Remove tests covered by sockmap_redir.

Signed-off-by: Michal Luczaj <mhal@rbox.co>
Signed-off-by: Martin KaFai Lau <martin.lau@kernel.org>
Acked-by: John Fastabend <john.fastabend@gmail.com>
Link: https://lore.kernel.org/r/20250515-selftests-sockmap-redir-v3-7-a1ea723f7e7e@rbox.co