Using wrong key value in engineInfo.closeWriters

[zimulala]

Bug Report

Please answer these questions before submitting your issue. Thanks!

1. Minimal reproduce step (Required)

tidb/ddl/ingest/engine.go

Lines 206 to 207 in ee758bc

	for wid := range ei.writerCache.Keys() {
	if w, ok := ei.writerCache.Load(wid); ok {

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

I think we want to get the key value.

3. What did you see instead (Required)

Get the sequence number.

4. What is your TiDB version? (Required)

Release Version: v6.6.0-alpha-306-g28d0325ae1-dirty
Edition: Community
Git Commit Hash: 28d0325ae12f080b978a147bba9f8467557019cd
Git Branch: master

[zimulala]

It will be fixed in #40542