ci-operator/templates/openshift/installer: Drop IMAGE_FORMAT

This image has been unused since the e2e template landed in 51df634
(Support an aws installer CI job, 2018-06-07, openshift#928) and since the
Ansible template landed in c35a30a (Add a profile openshift-ansible
custom AWS provisioner, 2018-08-30, openshift#1367).

Also remove the duplicated entry from the src template which landed in
aed67fc (Source installer tests should have access to IMAGE_FORMAT,
2019-01-25, openshift#2701).

ci-operator/templates/cluster-launch-e2e-openshift-ansible.yaml

@@ -9,8 +9,6 @@ parameters:
   required: true
 - name: NAMESPACE
   required: true
-- name: IMAGE_FORMAT
-  required: true
 - name: IMAGE_ANSIBLE
   required: true
 - name: IMAGE_TESTS

ci-operator/templates/openshift/installer/cluster-launch-installer-e2e.yaml

@@ -8,8 +8,6 @@ parameters:
   required: true
 - name: NAMESPACE
   required: true
-- name: IMAGE_FORMAT
-  required: true
 - name: IMAGE_INSTALLER
   required: true
 - name: IMAGE_TESTS

ci-operator/templates/openshift/installer/cluster-launch-installer-src.yaml

@@ -16,8 +16,6 @@ parameters:
   required: true
 - name: IMAGE_CLI
   required: true
-- name: IMAGE_FORMAT
-  required: true
 - name: IMAGE_TESTS
   required: true
 - name: CLUSTER_TYPE