test: use standard installer for e2e-iso

It contains UKIs now.

Signed-off-by: Andrey Smirnov <andrey.smirnov@siderolabs.com>

Author: smira

hack/test/e2e-iso.sh

@@ -9,8 +9,6 @@ CLUSTER_NAME=e2e-iso
 
 NODE="172.20.2.2"
 
-INSTALLER_IMAGE=${INSTALLER_IMAGE}-amd64-secureboot # we don't use secureboot part here, but this installer contains UKIs
-
 function create_cluster {
   build_registry_mirrors