Make REQUEST_NETWORK_SCORES signature only.

There are no use cases where it's needed by a privileged app today.

Test: Built and ran
BUG: 33752149
Change-Id: Ia63a86eca1f60644d25f037d395a08c541a06a08
Merged-In: Iae689e878fdb60b506536c918079a4fcff527a71