Remove DTRACE option

Enabling DTRACE option causes build failure.
It appears this option never really worked on FreeBSD.

PR: 217097
Submitted by: sunpoet (myself)
Approved by: Mikhail Tsatsenko <m.tsatsenko@gmail.com> (maintainer)
Thanks to: John Hein <z7dr6ut7gs@snkmail.com> (for analysis and testing)