sched: Fix sched_delayed vs sched_core

Completely analogous to commit dfa0a574 ("sched/uclamg: Handle
delayed dequeue"), avoid double dequeue for the sched_core entries.

Fixes: 152e11f6 ("sched/fair: Implement delayed dequeue")
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>