Remove dead code for AnomalyAlarm

Anomaly alarms now rely on the flow of events into statsd's socket for
firing alarms. Remove the StatsCompanionService code path, which is
unused now.

Test: m
Bug: 161326200
Bug: 152642091
Change-Id: Ife0b17c281984fc489ef46039cbf5aa7b1346bdb
Merged-In: Ife0b17c281984fc489ef46039cbf5aa7b1346bdb