cloud: update the default TiDB version of new TiDB Dedicated clusters

[Oreoxmt]

What is changed, added or deleted? (Required)

cloud: update the default TiDB version of new TiDB Dedicated clusters

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.

• [ ] master (the latest development version)
• [ ] v8.5 (TiDB 8.5 versions)
• [ ] v8.4 (TiDB 8.4 versions)
• [ ] v8.3 (TiDB 8.3 versions)
• [ ] v8.2 (TiDB 8.2 versions)
• [ ] v8.1 (TiDB 8.1 versions)
• [x] v7.5 (TiDB 7.5 versions)
• [ ] v7.1 (TiDB 7.1 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)

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

• This PR is translated from:
• 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

[Oreoxmt]

/hold

[ti-chi-bot[bot]]

[APPROVALNOTIFIER] This PR is NOT APPROVED

This pull-request has been approved by: Once this PR has been reviewed and has the lgtm label, please ask for approval from oreoxmt, ensuring that each of them provides their approval before proceeding. For more information see the Code Review Process.

The full list of commands accepted by this bot can be found here.

Needs approval from an approver in each of these files: - **[OWNERS](https://github.com/pingcap/docs/blob/release-7.5/OWNERS)** Approvers can indicate their approval by writing `/approve` in a comment Approvers can cancel approval by writing `/approve cancel` in a comment

[Oreoxmt]

/cc @Ivy-YinSu

[ti-chi-bot[bot]]

@Oreoxmt: GitHub didn't allow me to request PR reviews from the following users: Ivy-YinSu.

Note that only pingcap members and repo collaborators can review this PR, and authors cannot review their own PRs.

In response to [this](https://github.com/pingcap/docs/pull/19470#issuecomment-2493195235): >/cc @Ivy-YinSu Instructions for interacting with me using PR comments are available [here](https://git.k8s.io/community/contributors/guide/pull-requests.md). If you have questions or suggestions related to my behavior, please file an issue against the [kubernetes-sigs/prow](https://github.com/kubernetes-sigs/prow/issues/new?title=Prow%20issue:) repository.

[ti-chi-bot[bot]]

@yinsustart: adding LGTM is restricted to approvers and reviewers in OWNERS files.

In response to [this](https://github.com/pingcap/docs/pull/19470#pullrequestreview-2453696787): > Instructions for interacting with me using PR comments are available [here](https://git.k8s.io/community/contributors/guide/pull-requests.md). If you have questions or suggestions related to my behavior, please file an issue against the [kubernetes-sigs/prow](https://github.com/kubernetes-sigs/prow/issues/new?title=Prow%20issue:) repository.