chore(ci): ignore private repositories (esp. backstage app, backend) when release plugins

[christoph-jerolimov]

Hey, I just made a Pull Request!

This is a follow-up on #1510

It adds the missing changeset option privatePackages to new plugins so that their packages (backstage app and backend) are ignored when new releases are published.

  "privatePackages": {
    "tag": false,
    "version": false
  }

✔️ Checklist

• A changeset describing the change and affected packages. (more info)
• Added or updated documentation
• Tests for new functionality and regression tests for bug fixes
• Screenshots attached (for UI changes)
• All your commits have a Signed-off-by line in the message. (more info)

[awanlin]

Thanks for this follow up @christoph-jerolimov 🚀

[awanlin]

Oh, is it safe for me to merge?

[christoph-jerolimov]

All fine 🤗