Remove the root list of YAML manifests stored in manifests/

The root manifest directory was needed by the openshift
cluster-version-operator (CVO) to deploy OLM in OCP cluster
environments. During the 4.8 release, the
operator-framework/operator-lifecycle-manager was decoupled from the OCP
release cadence, and a downstream repository was created in the
openshift organization. As a result of this effort, these list of
manifests are no longer needed and instead will live in the downstream
repository.

Signed-off-by: timflannagan <[email protected]>

Author: timflannagan