Delete non-gprd Cloudflare exporter deployments

There is only one Cloudflare, and currently all deployments of the Cloudflare exporter (gprd, gstg, pre) have the same configuration. The non-gprd ones are arguably not needed, as k8s-dependent config (of which there is hardly any, just the deployment manifest) can be tested in minikube. We can reverse this decision in the future if a gstg deployment is considered useful.

Blocked on the ability to deploy k8s workloads to some, not all, environments. I'm not sure if theres an issue for that already, but this was spawned by https://gitlab.com/gitlab-com/gl-infra/k8s-workloads/monitoring/-/merge_requests/61#note_293326019.

cc @skarbek @bjk-gitlab