Remove Context.NETWORK_POLICY_SERVICE from @SystemApi

Hide Context.NETWORK_POLICY_SERVICE as it has no usage.

Bug: 151266974
Test: make checkapi, build
Copy from ag/10796415
Change-Id: I0586a5ef22f76fa1407219b96cb246f162f02947
Merged-In: I0586a5ef22f76fa1407219b96cb246f162f02947
2 files changed