Add a note about grpc-compression-type. (#6475)

[ti-chi-bot]

This is an automated cherry-pick of #6475

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• v5.1 (TiDB 5.1 versions)
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• This PR is translated from:
• Other reference link(s): 5.0.2 upgrade to 5.1.0, "sql analyze" in dashboard keep running, no result reported tidb#25419

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• Delete files
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• Need modification after applied to another branch
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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: 1a2ff6c