sched/fair: Remove unused 'curr' argument from pick_next_entity()

The 'curr' argument of pick_next_entity() has become unused after
the EEVDF changes.

[ mingo: Updated the changelog. ]

Signed-off-by: Yiwei Lin <s921975628@gmail.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lore.kernel.org/r/20231020055617.42064-1-s921975628@gmail.com