fix: add missing require import in schedule migration test (#9829)

## Summary
- Adds missing `github.com/stretchr/testify/require` import to
`tests/schedule_migration_test.go`
- The standalone test function
`TestScheduleMigrationV1ToV2NoDuplicateRecentActions` used
`require.NoError`, `require.Eventually`, and `require.Equal` without
importing the package, causing a build failure

Author: chaptersix

tests/schedule_migration_test.go

@@ -8,6 +8,7 @@ import (
 	"time"
 
 	"github.com/google/uuid"
+	"github.com/stretchr/testify/require"
 	commonpb "go.temporal.io/api/common/v1"
 	enumspb "go.temporal.io/api/enums/v1"
 	schedulepb "go.temporal.io/api/schedule/v1"