fix: do not run fe-islands jobs even in predictive pipelines

What does this MR do and why?

The MR ensures that FE islands' "preflight" jobs are not running in predictive not-ee pipelines.

References

• The example of the problematic pipeline: https://gitlab.com/gitlab-org/gitlab/-/pipelines/2179748360+. Not the failed start-as-if-foss due to fe-island jobs in the "preflight" stage of that child pipeline
• The example of the same MR as above, but with the fix, introduced in this MR (cherry-picked commit): https://gitlab.com/gitlab-org/gitlab/-/pipelines/2180157823+. Note that start-as-if-foss succeeds without creating the FE islands jobs in the "preflight" stage (actually the stage isn't created at all here, because there are no jobs to run there)