Fix Terraform error when importing GitLab project to infra-mgmt

Description:

When importing existing GitLab projects into Terraform in infra-mgmt, the plan looks as expected but when applying it fails due to an approval rule already existing. Error:

╷
│ Error: POST https://gitlab.com/api/v4/projects/41840368/approval_rules: 400 {message: {rule_type: [any-approver for the project already exists]}}
│ 
│   with module.project_gitlab_dedicated_managed_repos["aws-instance-health-exporter"].gitlab_project_approval_rule.approval["CODEOWNERS"],
│   on .terraform/modules/project_gitlab_dedicated_managed_repos/approvals.tf line 2, in resource "gitlab_project_approval_rule" "approval":
│    2: resource "gitlab_project_approval_rule" "approval" {
│

Example MRs to workaround by manually importing the rules:

This has happened at least three times, and seems to be an issue with the provider. It's become a bit of a papercut each time it happens when adding a project into infra-mgmt, so we should look into fixing it.

Provider resources:

if an "any_approver" rule is already present on a project at creation time, and that rule requires 0 approvers, the rule will be automatically imported to prevent a common error with this resource

One option is to set the any_approver rule to 0 approvers before importing to terraform, but that doesn't prevent us from hitting this again in the future. 🤔

Edited by Donna Alexandra