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First-time contributors' checklist

• I've signed Contributor License Agreement that's required for repo owners to accept my contribution.

What is changed, added, or deleted? (Required)

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

Since December 23, 2021, the TiDB DM documentation in the master branch has been merged to TiDB documentation by #8042 and #7317. To create a PR for TiDB DM versions later than v5.3, either go to TiDB English documentation repository or Chinese documentation repository.

• v5.3 (TiDB DM 5.3 versions)
• v2.0 (TiDB DM 2.0 versions)
• v1.0 (TiDB DM 1.0 versions)

What is the related PR or file link(s)?

• This PR is translated from:
• Other reference link(s):

Do your changes match any of the following descriptions?

• Delete files
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• Need modification after applied to another branch
• Might cause conflicts after applied to another branch

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