[CQ] migrate off slated-for-removal SystemInfo access

[pq]

https://plugins.jetbrains.com/plugin/9212-flutter/edit/versions/dev/909537#verification-results

I'm pretty sure this is behavior-preserving but could use another set of eyes.

---

• I’ve reviewed the contributor guide and applied the relevant portions to this PR.

Contribution guidelines:

• See our [contributor guide](https://github.com/flutter/flutter/blob/main/docs/contributing/Tree-hygiene.md for general expectations for PRs.
• Larger or significant changes should be discussed in an issue before creating a PR.
• Dart contributions to our repos should follow the Dart style guide and use dart format.
• Java and Kotlin contributions should strive to follow Java and Kotlin best practices (discussion).