statistics: update the note for sampling rate

[qiancai]

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• This PR is translated from: statistics: update the note for sampling rate docs-cn#17467
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[LGTM Timeline notifier]

Timeline:

• 2024-06-04 07:11:42.527776283 +0000 UTC m=+3365256.284911856: ☑️ agreed by Oreoxmt.

[qiancai]

/approve

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[ti-chi-bot]

In response to a cherrypick label: new pull request created to branch release-7.6: #17746.

[ti-chi-bot]

In response to a cherrypick label: new pull request created to branch release-8.0: #17747.

[ti-chi-bot]

In response to a cherrypick label: new pull request created to branch release-8.1: #17748.