cdc/sink: remove Initialize method from the sink interface (#3682)

[ti-chi-bot]

This is an automated cherry-pick of #3682

What problem does this PR solve?

This PR remove the Initialized method from the sink, which is useless.

What is changed and how it works?

Check List

Tests

• No code

Code changes

Side effects

Related changes

Release note

 `None`.

[ti-chi-bot]

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[ti-chi-bot]

@ti-chi-bot: This cherry pick PR is for a release branch and has not yet been approved by release team.
Adding the do-not-merge/cherry-pick-not-approved label.

To merge this cherry pick, it must first be approved by the collaborators.

AFTER it has been approved by collaborators, please ping the release team in a comment to request a cherry pick review.

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