Cleanup config_mobile_hotspot_provision_app usage

config_mobile_hotspot_provision_app would be move out of framework and
only private for tethering only.
enforceTetherChangePermission is no longer needed because its only
caller PanService already gate by other privileged permission
(BLUETOOTH_PRIVILEGED).

Bug: 146918263
Test: m

Change-Id: I030871c2bc46bc09c4e52970b4995f98d31bb90e