sysutils/reptyr: allow building on aarch64 as well

reptyr has technically supported FreeBSD/arm* since 0.10.0 was released
in June 2023; loosen up the build restrictions to build on arm64 now.

armv7 should also work fine, but I don't have any native armv7 around
to test that -- it doesn't work under COMPAT32 on aarch64, but I suspect
that's a ptrace(2) bug/shortcoming rather than reptyr failing on 32-bit
ARM.

PR: 285161
Approved by: maintainer timeout (2+ weeks, andoriyu@gmail.com)