[ALPS03804621] [P migration] Remove old property label

We never use persist.ril.* at Android P. So, remove it.

MTK-Commit-Id: 6a1943658ce7647e6efd65234252d69e83be1a47

Change-Id: I49d35e81192dfd9707687400bc3f0885cde16940
CR-Id: ALPS03804621
Feature: DSDS (Dual SIM Dual Standby) Framework-Common Framework(RIL)