runtime: switch FreeBSD to use the non-COMPAT_FREEBSD11 version of the kevent syscall

runtime: switch FreeBSD to use the non-COMPAT_FREEBSD11 version of the kevent syscall

Update #53280

Change-Id: I1c8d4510fbe8bdfe9a41575bde54ea2fbf6b67e9
Reviewed-on: https://go-review.googlesource.com/c/go/+/413174
Reviewed-by: Dmitri Goutnik <dgoutnik@gmail.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Bryan Mills <bcmills@google.com>
Reviewed-by: Ian Lance Taylor <iant@google.com>
Run-TryBot: Yuval Pavel Zholkover <paulzhol@gmail.com>