Remove openapi file

operator-sdk no longer generates the openapi file[1], so remove it from the
repo. If we want to continue offering it, we'll need to use openapi-gen
directly[2].

[1] operator-framework/operator-sdk#2276
[2] https://github.com/kubernetes/kube-openapi

Signed-off-by: James Slagle <jslagle@redhat.com>

Author: slagle