ticdc: refine faq doc (#20547)

[ti-chi-bot]

This is an automated cherry-pick of #20547

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• This PR is translated from: ticdc: refine faq doc docs-cn#20028
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• Delete files
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• Might cause conflicts after applied to another branch

[ti-chi-bot]

@qiancai This PR has conflicts, I have hold it.
Please resolve them or ask others to resolve them, then comment /unhold to remove the hold label.

[qiancai]

/approve

[qiancai]

/approve

[ti-chi-bot]

[APPROVALNOTIFIER] This PR is APPROVED

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