Remove isProvisioningNeededButUnavailable usage

config_mobile_hotspot_provision_app would be move out of framework and
only private for tethering only. TetherUtil#isProvisioningNeeded and
isProvisioningNeededButUnavailable are no longer needed because
tethering would ensure entitlement app is valid if entitlement check is
needed. Otherwise, tethering would return not supported that tethering
settings would be hidden.

Bug: 146918263
Test: m
Change-Id: If0b0a3e6cadab3c4a4d2c003e2aa9e9f3dd7449c