ctl: add a note for all ctl docs (#5435)

[ti-srebot]

cherry-pick #5435 to release-3.0
You can switch your code base to this Pull Request by using git-extras:

# In docs repo:
git pr https://github.com/pingcap/docs/pull/5509

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

git push [email protected]:ti-srebot/docs.git pr/5509:release-3.0-70a6d90f62c0

---

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

What is changed, added or deleted? (Required)

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

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• v5.0 (TiDB 5.0 versions)
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What is the related PR or file link(s)?

• This PR is translated from: ctl: add a note for all ctl docs docs-cn#6096
• 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

[ti-srebot]

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

[TomShawn]

/lgtm

[ti-chi-bot]

[REVIEW NOTIFICATION]

This pull request has been approved by:

• TomShawn

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[TomShawn]

/merge

[ti-chi-bot]

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

Commit hash: 28ef4eb