fix: pin ose-operator-registry image

Pin to specific image digest in all OPM tasks. Do not rely on floating
tags for reproducibility.

Signed-off-by: Martin Basti <mbasti@redhat.com>

Author: Martin Basti

task/opm-get-bundle-version/0.1/opm-get-bundle-version.yaml

@@ -20,7 +20,7 @@ spec:
     imagePullPolicy: IfNotPresent
   steps:
     - name: opm-render-bundle
-      image: "registry.redhat.io/openshift4/ose-operator-registry:latest"
+      image: "registry.redhat.io/openshift4/ose-operator-registry:latest@sha256:fb659a4c2942db5f1073c6b66be5c7ac2e4aed30432cce4aff08b9d5874010e9"
       securityContext:
         runAsUser: 0
       env:

task/opm-render-bundles/0.1/opm-render-bundles.yaml

@@ -27,7 +27,7 @@ spec:
     imagePullPolicy: IfNotPresent
   steps:
     - name: opm-render-bundles
-      image: "registry.redhat.io/openshift4/ose-operator-registry:latest"
+      image: "registry.redhat.io/openshift4/ose-operator-registry:latest@sha256:fb659a4c2942db5f1073c6b66be5c7ac2e4aed30432cce4aff08b9d5874010e9"
       workingDir: $(workspaces.source.path)/source
       securityContext:
         runAsUser: 0