Update `admin_merge_request_approval_settings` permissions

Following up this #374607 (comment 1172443559) about the change of permission alignment for OWNER and MAINTAINER role in groups and projects.

The policy admin_merge_request_approval_settings is not aligned for OWNER and MAINTAINER role in groups and projects. As group settings can be updated only by group owners whereas projects settings can be updated by project maintainers.

The feature will need to be updated so that only project owners can update project settings.