correct a tikv config name (#6073)

[ti-srebot]

cherry-pick #6073 to release-4.0
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# In docs-cn repo:
git pr https://github.com/pingcap/docs-cn/pull/6111

After apply modifications, you can push your change to this PR via:

git push git@github.com:ti-srebot/docs-cn.git pr/6111:release-4.0-f3e2aa26d858

---

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• I've signed Contributor License Agreement that's required for repo owners to accept my contribution.

What is changed, added or deleted? (Required)

ttl-poll-check-interval -> ttl-check-poll-interval
mysql> show config; | tikv | 10.186.1.1:20160 | storage.ttl-check-poll-interval | 12h

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

• master (the latest development version)
• 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)

[ti-chi-bot]

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[ti-srebot]

@sticnarf you're already a collaborator in bot's repo.

[TomShawn]

/close

[ti-chi-bot]

@TomShawn: Closed this PR.

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In response to this:

/close

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[TomShawn]

/unassign @sticnarf