multiple AZs in two regions: fix the topology example

[Oreoxmt]

What is changed, added or deleted? (Required)

The replication.location-labels configuration in three-data-centers-in-two-cities-deployment.md is inaccurate.

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[ti-chi-bot]

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• lilin90

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[Oreoxmt]

@nolouch PTAL

[nolouch]

What is the replication zone?

[nolouch]

it's better use like "region","zone","host".

[Oreoxmt]

The replication zone label is used here:

docs-cn/three-data-centers-in-two-cities-deployment.md

Lines 100 to 117 in b4eff71

	tikv_servers:
	- host: 10.63.10.30
	config:
	server.labels: { az: "1", replication zone: "1", rack: "1", host: "30" }
	- host: 10.63.10.31
	config:
	server.labels: { az: "1", replication zone: "2", rack: "2", host: "31" }
	- host: 10.63.10.32
	config:
	server.labels: { az: "2", replication zone: "3", rack: "3", host: "32" }
	- host: 10.63.10.33
	config:
	server.labels: { az: "2", replication zone: "4", rack: "4", host: "33" }
	- host: 10.63.10.34
	config:
	server.labels: { az: "3", replication zone: "5", rack: "5", host: "34" }
	raftstore.raft-min-election-timeout-ticks: 1000
	raftstore.raft-max-election-timeout-ticks: 1200

[lilin90]

LGTM

[qiancai]

Removed the needs-cherry-pick-release-6.4 label because the v6.4 docs have been archived at https://docs-archive.pingcap.com/zh/tidb/v6.4 and will no longer receive new updates.

[qiancai]

Removed the needs-cherry-pick-release-6.6 label because the v6.6 docs have been archived at https://docs-archive.pingcap.com/zh/tidb/v6.6 and will no longer receive new updates.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Removed the needs-cherry-pick-release-7.0 label because the v7.0 docs have been archived at https://docs-archive.pingcap.com/zh/tidb/v7.0 and will no longer receive new updates.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Removed the needs-cherry-pick-release-7.2 label because the v7.2 docs have been archived at https://docs-archive.pingcap.com/zh/tidb/v7.2 and will no longer receive new updates.

[ti-chi-bot]

PR needs rebase.

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