[MS64] Remove subscriberId and NetworkId in proto

netstats.proto is about to move into mainline module.
And it can no longer see privacy.proto definition.
Thus, this change remove PII data that is not very useful
when debugging and any reference to privacy.proto.

Test: adb bugreport and check output at transponder
Bug: 204830222
Change-Id: I755530f356d2c16b336d62785c4c17c557f792db