Remove the setDataTransfer API.

This API does not provide any additional value since we will now be
considering user-initiated data-transfer jobs as a combination of the
setUserInitiated and setRequiredNetworkType APIs instead.

Bug: 255371817
Test: atest JobSchedulerServiceTest
Test: atest JobStatusTest
Test: atest PendingJobQueueTest
Test: atest FlexibilityControllerTest
Change-Id: I732a2b9e1531d57ea33b9789b981ac861c3ff941