sched/fair: Remove check against

Checking that util_avg at dequeue is lower than the current CPU's max
capacity comes after the check that util_est is lower than
If util_est is lower than current util_avg at dequeue, util_est is
updated with the util_avg value. Otherwise if util_avg at dequeue is
checked against current CPU's max capacity.

In this order, if the util_avg at dequeue is higher than current CPU's max
capacity, util_est is updated.
Remove the check as the case is not possible.

The initial change was introduced by:
commit b8c96361 ("sched/fair/util_est: Implement faster ramp-up EWMA on utilization increases")

Signed-off-by: Pierre Gondois <pierre.gondois@arm.com>