pin gitlab-runner version in helm values
This change explicitly pins the gitlab-runner version tag in the gitlab-runners/values.yaml. This value can be used to do version upgrades. This is needed for SRE to bump the version for security upgrades.
See also https://gitlab.com/gitlab-org/charts/gitlab-runner/blob/main/values.yaml#L14
This should be noop, but I'm happy to assist merging if needed
kubectl get pods -n gitlab-runner -o jsonpath="{.items[*].spec.containers[*].image}" -l app=gitlab-runner
registry.gitlab.com/gitlab-org/gitlab-runner:alpine-v15.6.1