dm: update headings and minor errors

[ran-huang]

What is changed, added or deleted? (Required)

as title.

Which TiDB version(s) do your changes apply to? (Required)

Tips for choosing the affected version(s):

By default, CHOOSE MASTER ONLY so your changes will be applied to the next TiDB major or minor releases. If your PR involves a product feature behavior change or a compatibility change, CHOOSE THE AFFECTED RELEASE BRANCH(ES) AND MASTER.

For details, see tips for choosing the affected versions.

• [x] master (the latest development version)
• [ ] v6.3 (TiDB 6.3 versions)
• [x] v6.1 (TiDB 6.1 versions)
• [ ] v5.4 (TiDB 5.4 versions)
• [ ] v5.3 (TiDB 5.3 versions)
• [ ] v5.2 (TiDB 5.2 versions)
• [ ] v5.1 (TiDB 5.1 versions)
• [ ] v5.0 (TiDB 5.0 versions)

[ti-chi-bot]

[REVIEW NOTIFICATION]

This pull request has been approved by:

• lilin90

To complete the pull request process, please ask the reviewers in the list to review by filling /cc @reviewer in the comment. After your PR has acquired the required number of LGTMs, you can assign this pull request to the committer in the list by filling /assign @committer in the comment to help you merge this pull request.

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[ran-huang]

/merge

[ti-chi-bot]

This pull request has been accepted and is ready to merge.

Commit hash: a7c536fdf9ce357715dde64300b36d134d5e1d5c

[ti-chi-bot]

In response to a cherrypick label: new pull request created: #11016.

[ti-chi-bot]

In response to a cherrypick label: new pull request created: #11017.

[ti-chi-bot]

In response to a cherrypick label: new pull request created: #11018.