Update deprecated argument

│ Warning: Argument is deprecated
│ 
│   with module.customer_projects.gitlab_project.project["test-dev-access"],
│   on .terraform/modules/customer_projects/project/main.tf line 25, in resource "gitlab_project" "project":
│   25:   approvals_before_merge                           = each.value.approvals_before_merge
│ 
│ Use the resource `gitlab_project_approval_rule` instead. To be removed in
│ 19.0.