Enable FF_RETRIEVE_POD_WARNING_EVENTS by default

!4211 (merged) was added to diagnose job failures due to Kubernetes killing a pod, but it is disabled by default.

This might have helped triage https://gitlab.com/gitlab-com/ops-sub-department/section-ops-request-for-help/-/issues/364.

Does this require watch permission to be enabled as mentioned in #36961 (closed)?