hexdump: Remove expected test failures for now succeeding tests

r323990 fixed the -s flag breakage reported by PR 219173. Mark the
corresponding hexdump tests accordingly, since they should now both succeed.

PR: 222781
Reported by: ngie
Reviewed by: emaste, ngie
Approved by: emaste (mentor)
Differential Revision: https://reviews.freebsd.org/D12590