add image for closest-adaptive

[SunRunAway]

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[glorv]

LGTM

[qiancai]

Removed the needs-cherry-pick-release-6.6 label because the v6.6 docs have been archived at https://docs-archive.pingcap.com/tidb/v6.6 and will no longer receive new updates.

[qiancai]

Removed the needs-cherry-pick-release-7.0 label because the v7.0 docs have been archived at https://docs-archive.pingcap.com/tidb/v7.0 and will no longer receive new updates.

[qiancai]

Removed the needs-cherry-pick-release-7.2 label because the v7.2 docs have been archived at https://docs-archive.pingcap.com/tidb/v7.2 and will no longer receive new updates.

[qiancai]

Removed the needs-cherry-pick-release-7.3 label because the v7.3 docs have been archived at https://docs-archive.pingcap.com/tidb/v7.3 and will no longer receive new updates.