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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[codecov-commenter]

Codecov Report

❗ No coverage uploaded for pull request base (release-5.0@6e6af29). Click here to learn what that means.
The diff coverage is n/a.

@@               Coverage Diff                @@
##             release-5.0      #3762   +/-   ##
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[amyangfei]

/merge

[ti-chi-bot]

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

Commit hash: 69805cd

[3AceShowHand]

/run-kafka-integration-test

[ti-chi-bot]

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/run-all-tests

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