Now that precision propagation is supported fully in the presence of
subprogs, there is no need to work around iter test. Revert original
workaround.

This reverts be7dbd27 ("selftests/bpf: avoid mark_all_scalars_precise() trigger in one of iter tests").
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/r/20230505043317.3629845-11-andrii@kernel.orgSigned-off-by: Alexei Starovoitov <ast@kernel.org>