Document how approver permissions change when the list of approvers changes on an existing deployment

User problem

1. Set up deployment approvals with allowing members of a group to approve/deploy
2. Start a pipeline that creates a deployment
3. Change the group members

Can removed/new group members approve?

Proposal

Extend the documentation on https://docs.gitlab.com/ee/ci/environments/deployment_approvals.html#configure-deployment-approvals with answers to the above questions