toolforge-cd: only_helm_publish.yaml: add missing stage

The create_release.yaml include uses the 'release' stage but the declaration is missing here.

Because the deep merge strategy of gitlab CI for arrays, if an included yaml defines other stages in this array, they need to be repeated here too which may be a bit pointless, and/or even error prone... because you have to manually keep the arrays in sync.

See: https://docs.gitlab.com/ee/ci/yaml/includes.html#override-included-configuration-arrays

Another option would be to declare this list just once in a central place, and not here or in the inner 'function' includes. But let's do that refactor other day.

Signed-off-by: Arturo Borrero Gonzalez aborrero@wikimedia.org