fix some wrong statements in clustered-indexes.md (#5864)

[ti-srebot]

cherry-pick #5864 to release-5.0
You can switch your code base to this Pull Request by using git-extras:

# In docs-cn repo:
git pr https://github.com/pingcap/docs-cn/pull/5865

After apply modifications, you can push your change to this PR via:

git push git@github.com:ti-srebot/docs-cn.git pr/5865:release-5.0-160bfc8db9b6

---

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What is changed, added or deleted? (Required)

Fix some wrong statements in clustered-indexes.md

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

• master (the latest development version)
• 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)?

• This PR is translated from: NA
• Other reference link(s): Update clustered-indexes.md #5771, update the description related to clustered indexes #5834

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

[ti-srebot]

@tangenta you're already a collaborator in bot's repo.

[ti-chi-bot]

[REVIEW NOTIFICATION]

This pull request has been approved by:

• yikeke

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[yikeke]

/merge

[ti-chi-bot]

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

Commit hash: 12492e1