placement-rules-in-sql: add some lightning descriptions

[lcwangchao]

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• This PR is translated from: placement-rules-in-sql: add some lightning descriptions docs-cn#8853
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[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: 04a92b8

[ti-chi-bot]

In response to a cherrypick label: new pull request created: #8067.