Ensure runner projects are fetched in correct order in specs

What does this MR do and why?

This MR fixes a master-brokenflaky-test situation in spec/services/ci/runners/set_runner_associated_projects_service_spec.rb which caused gitlab-org/quality/engineering-productivity/master-broken-incidents#3390 (closed).

How to set up and validate locally

Numbered steps to set up and validate the change are strongly suggested.

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

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