tech(alerting): remove frequency from alert model

pkg/models/alert.go

@@ -16,7 +16,6 @@ type Alert struct {
 	State       string
 	Scheduler   int64
 	Enabled     bool
-	Frequency   int
 
 	Created time.Time
 	Updated time.Time

pkg/services/sqlstore/migrations/alert_mig.go

@@ -18,7 +18,6 @@ func addAlertMigrations(mg *Migrator) {
 			{Name: "state", Type: DB_NVarchar, Length: 255, Nullable: false},
 			{Name: "expression", Type: DB_Text, Nullable: false},
 			{Name: "scheduler", Type: DB_BigInt, Nullable: false},
-			{Name: "frequency", Type: DB_BigInt, Nullable: false},
 			{Name: "enabled", Type: DB_Bool, Nullable: false},
 			{Name: "created", Type: DB_DateTime, Nullable: false},
 			{Name: "updated", Type: DB_DateTime, Nullable: false},