Remove extra condition on cache secret
Removes the extra condition on mounting the Runner cache secret to better align with the original state prior to gitlab-org/charts/gitlab-runner!393 (merged) and gitlab-org/charts/gitlab-runner!406 (merged).
The Helm Charts override this template to include the MinIO Secret if MinIO is enabled.
Further context: gitlab-org/charts/gitlab-runner#460 (comment 1425750980)