fix ticdc docs

[asddongmen]

First-time contributors' checklist

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

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

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

• [x] master (the latest development version)
• [x] v1.5 (TiDB Operator 1.5 versions)
• [ ] v1.4 (TiDB Operator 1.4 versions)
• [ ] v1.3 (TiDB Operator 1.3 versions)
• [ ] v1.2 (TiDB Operator 1.2 versions)

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[ti-chi-bot[bot]]

[REVIEW NOTIFICATION]

This pull request has been approved by:

• ran-huang

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[ran-huang]

/merge /remove-status LGT1 /status LGT2

[ti-chi-bot[bot]]

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

Commit hash: 207c2339a6155e3825b7311b2dac64f68566ebe3

[ti-chi-bot]

In response to a cherrypick label: new pull request created to branch release-1.5: #2366.