error message of BR is misleading

[lance6716]

Bug Report

Please answer these questions before submitting your issue. Thanks!

1. Minimal reproduce step (Required)

tidb/br/pkg/restore/split.go

Lines 353 to 354 in 8e525d8

	return errors.Annotatef(berrors.ErrPDBatchScanRegion, "last region's endKey < startKey, startKey: %s, regionStartKey: %s",
	redact.Key(endKey), redact.Key(regions[len(regions)-1].Region.EndKey))

2. What did you expect to see? (Required)

last region's endKey < endKey, regionEndKey: %s, endKey: %s

3. What did you see instead (Required)

last region's endKey < startKey, startKey: %s, regionStartKey: %s

4. What is your TiDB version? (Required)

[github-actions]

Please check whether the issue should be labeled with 'affects-x.y' or 'fixes-x.y.z', and then remove 'needs-more-info' label.