Update customers_dot_zuora_error metric name
Closes gitlab-org/customers-gitlab-com#6626 (closed)
This MR renames the customers_dot_zuora_error
counter into customers_dot_zuora_error_total
.
Snapshot: https://dashboards.gitlab.net/dashboard/snapshot/rjfG0F19G12imhOSlk8Hp8xMeKTV6r34?orgId=1