Remove server version upgrade

[ran-huang]

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)

增加关于在升级过程中，对于 server-version 配置参数的说明。

updates for TiDB in K8s is included in pingcap/docs-tidb-operator#2431

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

Tips for choosing the affected version(s):

By default, CHOOSE MASTER ONLY so your changes will be applied to the next TiDB major or minor releases. If your PR involves a product feature behavior change or a compatibility change, CHOOSE THE AFFECTED RELEASE BRANCH(ES) AND MASTER.

For details, see tips for choosing the affected versions (in Chinese).

• master (the latest development version)
• v7.3 (TiDB 7.3 versions)
• v7.2 (TiDB 7.2 versions)
• v7.1 (TiDB 7.1 versions)
• v7.0 (TiDB 7.0 versions)
• v6.5 (TiDB 6.5 versions)
• v6.1 (TiDB 6.1 versions)
• v5.4 (TiDB 5.4 versions)
• v5.3 (TiDB 5.3 versions)
• v5.2 (TiDB 5.2 versions)
• v5.1 (TiDB 5.1 versions)
• v5.0 (TiDB 5.0 versions)

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

• This PR is translated from: Remove server version upgrade docs-cn#14569
• Other reference link(s):

Do your changes match any of the following descriptions?

• Delete files
• Change aliases
• Need modification after applied to another branch
• Might cause conflicts after applied to another branch

[ti-chi-bot]

[LGTM Timeline notifier]

Timeline:

• 2023-08-14 03:48:52.144412602 +0000 UTC m=+516496.693428574: ☑️ agreed by Oreoxmt.

[ran-huang]

/approve

[ti-chi-bot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: ran-huang

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[ti-chi-bot]

In response to a cherrypick label: new pull request created to branch release-7.3: #14500.

[ti-chi-bot]

In response to a cherrypick label: new pull request created to branch release-6.5: #14501.

[ti-chi-bot]

In response to a cherrypick label: new pull request created to branch release-7.0: #14502.

[ti-chi-bot]

In response to a cherrypick label: new pull request created to branch release-7.1: #14503.

[ti-chi-bot]

In response to a cherrypick label: new pull request created to branch release-7.2: #14504.