Merge Request Approval Widget: Show only users that have proper permissions to approve
### Problem to solve
Selecting a group to be associated with a Merge Request Approval policy shows all group individuals (guests) within the merge request approvers widget. (regardless of permissions/roles required to approve)
### Intended users
* [Cameron (Compliance Manager)](https://about.gitlab.com/handbook/marketing/product-marketing/roles-personas/#cameron-compliance-manager)
* [Parker (Product Manager)](https://about.gitlab.com/handbook/marketing/product-marketing/roles-personas/#parker-product-manager)
* [Delaney (Development Team Lead)](https://about.gitlab.com/handbook/marketing/product-marketing/roles-personas/#delaney-development-team-lead)
* [Sasha (Software Developer)](https://about.gitlab.com/handbook/marketing/product-marketing/roles-personas/#sasha-software-developer)
* [Devon (DevOps Engineer)](https://about.gitlab.com/handbook/marketing/product-marketing/roles-personas/#devon-devops-engineer)
* [Rachel (Release Manager)](https://about.gitlab.com/handbook/marketing/product-marketing/roles-personas/#rachel-release-manager)
### Proposal
- Only show individuals with Developer or higher permissions within the widget when associating a group within the merge request approvals policy. ([Approvals require Developer or high permissions](https://gitlab.com/help/user/project/merge_requests/merge_request_approvals#eligible-approvers))
### Links / references
PM: @danielgruesso
issue