refactor(go): drop redundant daily mileage vin index

go/vehicle-gateway/internal/stats/schema.go

@@ -10,7 +10,6 @@ const DailyMileageTableSQL = `CREATE TABLE IF NOT EXISTS vehicle_daily_mileage (
   sample_count BIGINT NOT NULL DEFAULT 0,
   updated_at DATETIME NOT NULL DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP,
   PRIMARY KEY (vin, stat_date, protocol),
-  KEY idx_vin (vin),
   KEY idx_stat_date (stat_date),
   KEY idx_protocol_date (protocol, stat_date)
 )`