sched/lapic: remove sched_do_timer_accounting()

The check is always true, especially after the removal of hlt_cpus_mask
from sched_4bsd.

Reviewed by: olce, kib
MFC after: 1 week
Sponsored by: The FreeBSD Foundation
Differential Revision: https://reviews.freebsd.org/D58159

(cherry picked from commit 01f165c68103df22cebe26d410c1d4a0e5fae377)