Dashboard Migrations: V4 - no-op and clean up dead code from DashboardMigrator.ts (#112225)

apps/dashboard/pkg/migration/schemaversion/v4.go

@@ -0,0 +1,9 @@
+package schemaversion
+
+import "context"
+
+// V4 is a no-op migration
+func V4(_ context.Context, dashboard map[string]interface{}) error {
+	dashboard["schemaVersion"] = 4
+	return nil
+}