Update supported OpenShift version (#52)

The Operator Bundle certification fails with any version < 4.8 with a message that syas they've reached its end of life

Author: lucacome

bundle.Dockerfile

@@ -20,6 +20,6 @@ COPY bundle/manifests /manifests/
 COPY bundle/metadata /metadata/
 COPY bundle/tests/scorecard /tests/scorecard/
 
-LABEL com.redhat.openshift.versions="v4.6"
+LABEL com.redhat.openshift.versions="v4.8"
 LABEL com.redhat.delivery.operator.bundle=true
 LABEL com.redhat.delivery.backport=true