tidb-ctl: fix decoder command

[ran-huang]

What is changed, added or deleted? (Required)

as title

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

• This PR is translated from:fix the usage of tidb-ctl decoder docs-cn#13386
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• Delete files
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• Might cause conflicts after applied to another branch

[ti-chi-bot]

[REVIEW NOTIFICATION]

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• Oreoxmt

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[Oreoxmt]

LGTM

[ran-huang]

/merge

[ti-chi-bot]

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

Commit hash: 681e4a4

[ti-chi-bot]

In response to a cherrypick label: new pull request created to branch release-6.1: #12881.

[ti-chi-bot]

In response to a cherrypick label: new pull request created to branch release-6.5: #12882.

[ti-chi-bot]

In response to a cherrypick label: new pull request created to branch release-6.6: #12883.