Clarify tidb lightning backend description

[Liuxiaozhen12]

What is changed, added or deleted? (Required)

Clarify tidb lightning backend description

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

• master (the latest development version)
• 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)?

• This PR is translated from: Clarify tidb lightning backend description docs-cn#6468
• 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-chi-bot]

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[Liuxiaozhen12]

/label needs-cherry-pick-release-5.0
/label needs-cherry-pick-release-4.0
/translation from-docs-cn

[ti-chi-bot]

@kennytm: 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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[TomShawn]

LGTM

[TomShawn]

/remove-status LGT1
/status LGT2

[TomShawn]

/merge

[ti-chi-bot]

In response to a cherrypick label: new pull request created: #5905.

[ti-chi-bot]

In response to a cherrypick label: new pull request created: #5906.

[TomShawn]

/run-cherry-picker

[ti-chi-bot]

@TomShawn: These labels are not set on the issue: status/lgt1.

Details

In response to this:

/remove-status LGT1
/status LGT2

Instructions for interacting with me using PR comments are available here. If you have questions or suggestions related to my behavior, please file an issue against the ti-community-infra/tichi repository.

[ti-chi-bot]

In response to a cherrypick label: new pull request created: #5907.

[ti-chi-bot]

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

Details

Commit hash: 460a768

[ti-chi-bot]

In response to a cherrypick label: new pull request could not be created: failed to create pull request against pingcap/docs#release-5.1 from head ti-chi-bot:cherry-pick-5904-to-release-5.1: status code 422 not one of [201], body: {"message":"Validation Failed","errors":[{"resource":"PullRequest","code":"custom","message":"A pull request already exists for ti-chi-bot:cherry-pick-5904-to-release-5.1."}],"documentation_url":"https://docs.github.com/rest/reference/pulls#create-a-pull-request"}