Improve "Preview Theme Changes" GitHub Actions workflow

[tfrommen]

This quick PR includes some general improvements for the preview workflow:

• Start with no permissions, then grant required permissions on job level.
• Specify timeout.
• Upgrade checkout action.
• Formatting.

[github-actions]

Preview changes

You can preview these changes by following the link below:

• Preview changes for twentytwentyfive

I will update this comment with the latest preview links as you push more changes to this PR.

Note

The preview sites are created using WordPress Playground. You can add content, edit settings, and test the themes as you would on a real site, but please note that changes are not saved between sessions.

[github-actions]

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Co-authored-by: tfrommen <tfrommen@git.wordpress.org>
Co-authored-by: carolinan <poena@git.wordpress.org>

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[carolinan]

Hi
Since this repository is going to be archived, I don't think there is any reason to update this.
The bundled themes are only built on GitHub until release. Normally, this archive would have been closed at RC1.