config(ticdc): fix deafult setting of DateSeparator (#9090)

[ti-chi-bot]

This is an automated cherry-pick of #9090

What problem does this PR solve?

Issue Number: ref #8824, ref #8997

What is changed and how it works?

fix deafult setting of DateSeparator

Check List

Tests

• Unit test
• Integration test

Questions

Will it cause performance regression or break compatibility?

Do you need to update user documentation, design documentation or monitoring documentation?

Release note

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[ti-chi-bot]

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