fix: correct whitespace usage

[Oreoxmt]

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What is changed, added or deleted? (Required)

fix: correct whitespace usage

The code blocks in the PDF are displayed incorrectly due to wrong whitespace usage:

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

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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.

• master (the latest development version)
• v7.3 (TiDB 7.3 versions)
• v7.2 (TiDB 7.2 versions)
• v7.1 (TiDB 7.1 versions)
• v7.0 (TiDB 7.0 versions)
• v6.5 (TiDB 6.5 versions)
• v6.1 (TiDB 6.1 versions)
• v5.4 (TiDB 5.4 versions)
• v5.3 (TiDB 5.3 versions)
• v5.2 (TiDB 5.2 versions)
• v5.1 (TiDB 5.1 versions)
• v5.0 (TiDB 5.0 versions)

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

• This PR is translated from: fix: correct whitespace usage docs-cn#14665
• Other reference link(s):

Do your changes match any of the following descriptions?

• Delete files
• Change aliases
• Need modification after applied to another branch
• Might cause conflicts after applied to another branch

[ran-huang]

rest LGTM

[ti-chi-bot]

[LGTM Timeline notifier]

Timeline:

• 2023-08-02 11:35:29.382878413 +0000 UTC m=+271613.325226937: ☑️ agreed by ran-huang.

[Oreoxmt]

/approve

[ti-chi-bot]

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