Fix `project_tree_restorer_spec` flakiness

What does this MR do?

Fix flaky spec.

The reason for flakiness:
In !18024 (merged), we added an additional Pipeline into the project.json import fixture: !18024 (diffs)

This pipeline has 0 stages, and not 2, like all others.

In the test, we are fetching @project.ci_pipelines where the order is not deterministic, which should be changed.

Does this MR meet the acceptance criteria?

Conformity

• [-] Changelog entry
• [-] Documentation created/updated or follow-up review issue created
• Code review guidelines
• Merge request performance guidelines
• Style guides
• Database guides
• Separation of EE specific content

Closes #35323 (closed)