fix: update image var

1 job for master in 39 seconds (queued for 3 seconds)
Status Name Job ID Coverage
  Build
failed build #47845

00:00:39

 
Name Stage Failure
failed
build Build
Error response from daemon: manifest for registry.gitlab.tpwd.de/cmmc-systems/docker-ftp:latest not found: manifest unknown: manifest unknown
$ docker build --cache-from $CI_REGISTRY_IMAGE:latest --tag $CI_REGISTRY_IMAGE:$CI_COMMIT_SHA --tag $CI_REGISTRY_IMAGE:latest -f $DOCKERFILE .
"docker build" requires exactly 1 argument.
See 'docker build --help'.

Usage: docker build [OPTIONS] PATH | URL | -

Build an image from a Dockerfile
ERROR: Job failed: exit code 1