Change default value of replicas from 2 to 1
The new runner registration workflow resulted in the following error:
Error: execution error at
(gitlab-runner/templates/deployment.yaml:28:31): Using a runner token
with more than 1 replica is not supported. with
module.gitlab.helm_release.this, on gitlab/main.tf line 16, in
resource "helm_release" "this": 16: resource "helm_release" "this" {
So we're reducing the number of replicas 1 until a better solution is
found.
Bug: T344951