Potential workaround for flaky spec in jobs_controller_spec.rb

ee/spec/controllers/ee/projects/jobs_controller_spec.rb appears to be flaky due to some intermittent issue with handling a GRPC::NotFound exception in a streaming response. Even the debugger has difficult following the flow: https://github.com/deivid-rodriguez/byebug/issues/725

The controller is attempting to lookup the ref of the pipeline commit. In the common case, repository would be there, and rendering a pipeline from a missing repository isn't normal. We work around the issue by just making sure the projects in the test have repositories.

Potential fix for #227845 (closed)