ticdc: Fix cdc doc outdate link and info

[3AceShowHand]

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What is changed, added or deleted? (Required)

• fix outdated cdc golang demo link
• fix outdated recommand disk information.

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• master (the latest development version)
• v5.1 (TiDB 5.1 versions)
• v5.0 (TiDB 5.0 versions)
• v4.0 (TiDB 4.0 versions)
• v3.1 (TiDB 3.1 versions)
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• v2.1 (TiDB 2.1 versions)

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Do your changes match any of the following descriptions?

• Delete files
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[ti-chi-bot]

[REVIEW NOTIFICATION]

This pull request has been approved by:

• TomShawn
• amyangfei

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[TomShawn]

/merge

[ti-chi-bot]

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

Commit hash: bfef4b8

[ti-chi-bot]

In response to a cherrypick label: new pull request created: #6771.

[ti-chi-bot]

In response to a cherrypick label: new pull request created: #6772.

[ti-chi-bot]

In response to a cherrypick label: new pull request created: #6773.