[security] SubscriptionGroup is exposed to unprivileged callers

SubscriptionInfo.mGroupUUID is not cleared in
conditionallyRemoveIdentifiers if the caller only has READ_PHONE_STATE
(based on a check to checkReadPhoneState) and not READ_DEVICE_IDENTIFIERS.
Bug: 181053462
Test: atest SubscriptionManagerTest

Change-Id: Ic2b62523330dc6e2169ad851715c4ab3da3b29cf
Merged-In: Ic2b62523330dc6e2169ad851715c4ab3da3b29cf
(cherry picked from commit 219d284a68f56093aa9ca6610a4999b35c4cf5a9)