Remove the high priority min execution limit.

The separate limit was added as a way to discourage setting all jobs to
high priority, but would only make things confusing and JobScheduler's
logic more complicated. Remove it so that all regular jobs, including
downgraded expedited jobs and user-initiated jobs have the same min
limit.

Bug: 141645789
Test: atest FrameworksMockingServicesTests:JobSchedulerServiceTest
Change-Id: Ic27866366b3794158f48d960277f8412ff78ee2f