Do not run check-envtest-existing packages concurrently
Do not run check-envtest-existing packages concurrently

The "check-envtest-existing" target runs all tests against a single
Kubernetes cluster. The test setup provided by "envtest.Environment"
cannot be run concurrently with itself because it touches non-namespaced
resources (CRDs).

Issue: [sc-12657]

CrunchyData/postgres-operator,CrunchyData/postgres-operator