bsd.own.mk: Assume a modern make

Commit 83cb5bae966d7 added a check for MAKE_VERSION being new enough to
handle CTFCONVERT_CMD being an empty string since fmake of the time
didn't support it until just a few commits before 83cb5bae966d7. Later,
it was augmented with a check for .PARSEDIR to see if bmake was
running. fmake and boostrapping from fmake haven't worked in maybe 6 or
8 years, so we can remove the check here. If you want to update from
your FreeBSD 7 or FreeBSD 8 systems, you're even more out of luck than
you were before and must jump to an older version before jumping to
current for the source upgrade path.

Sponsored by: Netflix
Reviewed by: brooks, emaste
Pull Request: https://github.com/freebsd/freebsd-src/pull/980