doc: add more details to grpc-compression configs

[ekexium]

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[ti-chi-bot]

[LGTM Timeline notifier]

Timeline:

• 2024-07-18 03:53:43.357119186 +0000 UTC m=+498845.348060649: ☑️ agreed by overvenus.
• 2024-07-23 09:45:06.299720664 +0000 UTC m=+951928.290662134: ☑️ agreed by qiancai.

[qiancai]

/approve

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[ti-chi-bot]

In response to a cherrypick label: new pull request created to branch release-8.2: #18090.