remove variable START_OFFSET_NANOS
remove variable START_OFFSET_NANOS

Remove variable START_OFFSET_NANOS as it never used

computationalEpidemiology/biobankAccelerometerAnalysis,aidendoherty/biobankAccelerometerAnalysis,aidendoherty/biobankAccelerometerAnalysis,computationalEpidemiology/biobankAccelerometerAnalysis