Fix a typo in sync diff

[Rustin170506]

Signed-off-by: hi-rustin rustin.liu@gmail.com

First-time contributors' checklist

• I've signed Contributor License Agreement that's required for repo owners to accept my contribution.

What is changed, added or deleted? (Required)

Fix a typo in sync diff.

Which TiDB version(s) do your changes apply to? (Required)

Tips for choosing the affected version(s):

By default, CHOOSE MASTER ONLY so your changes will be applied to the next TiDB major or minor releases. If your PR involves a product feature behavior change or a compatibility change, CHOOSE THE AFFECTED RELEASE BRANCH(ES) AND MASTER.

For details, see tips for choosing the affected versions (in Chinese).

• master (the latest development version)
• v5.3 (TiDB 5.3 versions)
• v5.2 (TiDB 5.2 versions)
• v5.1 (TiDB 5.1 versions)
• v5.0 (TiDB 5.0 versions)
• v4.0 (TiDB 4.0 versions)
• v3.1 (TiDB 3.1 versions)
• v3.0 (TiDB 3.0 versions)
• v2.1 (TiDB 2.1 versions)

What is the related PR or file link(s)?

close #7906

• This PR is translated from:
• Other reference link(s):

Do your changes match any of the following descriptions?

None

[ti-chi-bot]

[REVIEW NOTIFICATION]

This pull request has been approved by:

• TomShawn
• shichun-0415

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[Rustin170506]

/cc @Leavrth
Could you please take a look? Thanks! 💚 💙 💜 💛 ❤️

[ti-chi-bot]

@Leavrth: Thanks for your review. The bot only counts approvals from reviewers and higher roles in list, but you're still welcome to leave your comments.

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[hfxsd]

/merge

[ti-chi-bot]

@hfxsd: /merge in this pull request requires 2 approval(s).

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/merge

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[shichun-0415]

LGTM

[hfxsd]

/merge

[ti-chi-bot]

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

Commit hash: 3e98a93

[ti-chi-bot]

In response to a cherrypick label: new pull request created: #7932.