update preflight sha for 1.18.0 release (#949)

Signed-off-by: Adam D. Cornett <adc@redhat.com>

Author: acornett21

ansible/roles/operator-pipeline/templates/openshift/tasks/preflight.yml

@@ -7,7 +7,7 @@ spec:
   params:
     - name: pipeline_image
     - name: base_image
-      default: quay.io/redhat-isv/preflight-test@sha256:2f9816292f4dec166c03d913d7e8b9673f9313bc5220a5b82efb0923b81095b1
+      default: quay.io/redhat-isv/preflight-test@sha256:6dc9402d20c330e693e6a949ab42c8721e385f012379ff99d51310ec1cbef576
       description: Preflight image used
     - name: bundle_index_image
       description: The Operator index image which includes the bundle