selftests/bpf: specify pahole version requirement for btf_tag test

Specify pahole version requirement (1.23) for btf_tag subtests
btf_type_tag_user_{mod1, mod2, vmlinux}.

Signed-off-by: Yonghong Song <yhs@fb.com>
Link: https://lore.kernel.org/r/20220127154622.663337-1-yhs@fb.com


Signed-off-by: Alexei Starovoitov <ast@kernel.org>