workqueue: Avoid nr_active manipulation in grabbing inactive items

Current try_to_grab_pending() activates the inactive item and
subsequently treats it as though it were a standard activated item.

This approach prevents duplicating handling logic for both active and
inactive items, yet the premature activation of an inactive item
triggers trace_workqueue_activate_work(), yielding an unintended user
space visible side effect.

And the unnecessary increment of the nr_active, which is not a simple
counter now, followed by a counteracted decrement, is inefficient and
complicates the code.

Just remove the nr_active manipulation code in grabbing inactive items.

Signed-off-by: Lai Jiangshan <jiangshan.ljs@antgroup.com>
Signed-off-by: Tejun Heo <tj@kernel.org>