en,zh: bump operator to v1.6.0

[csuzhangxc]

First-time contributors' checklist

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

What is changed, added, or deleted? (Required)

find . -type f | xargs sed -i "s/v1.6.0-beta.1/v1.6.0/g"
git checkout -- zh/releases en/releases

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

• master (the latest development version)
• v1.6 (TiDB Operator 1.6 versions)
  • expect this can be cherry-picked to v1.6
• v1.5 (TiDB Operator 1.5 versions)
• v1.4 (TiDB Operator 1.4 versions)
• v1.3 (TiDB Operator 1.3 versions)
• v1.2 (TiDB Operator 1.2 versions)

What is the related PR or file link(s)?

• This PR is translated from:
• Other reference link(s):

[ti-chi-bot]

[LGTM Timeline notifier]

Timeline:

• 2024-05-27 06:41:45.569231778 +0000 UTC m=+2672259.326367351: ☑️ agreed by Oreoxmt.
• 2024-05-27 08:22:05.603024624 +0000 UTC m=+2678279.360160189: ☑️ agreed by qiancai.

[Oreoxmt]

/approve

[ti-chi-bot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: Oreoxmt

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[ti-chi-bot]

In response to a cherrypick label: new pull request created to branch release-1.6: #2577.