Fix MR approval form showing in free plan

`requires_approve?` went through several iterations,
earliest one implies license by checking `approvals_required.nonzero?`.
This was however set to true so caused EE specific UI to appear by
mistake.

ee/app/views/shared/issuable/_approvals.html.haml

@@ -3,7 +3,7 @@
 - form = local_assigns.fetch(:form)
 
 - return unless issuable.is_a?(MergeRequest)
-- return unless presenter.requires_approve?
+- return unless @project.feature_available?(:merge_request_approvers)
 
 - can_update_approvers = can?(current_user, :update_approvers, issuable)
 

ee/changelogs/unreleased/9908-hide-approver-ui-in-free.yml

+---
+title: Fix approval-related UI showing up in free plan
+merge_request: 9819
+author:
+type: fixed

ee/spec/views/shared/issuable/_approvals.html.haml_spec.rb

@@ -15,7 +15,6 @@ describe 'shared/issuable/_approvals.html.haml' do
     allow(view).to receive(:current_user).and_return(user)
     allow(form).to receive(:label)
     allow(form).to receive(:number_field)
-    allow(merge_request).to receive(:requires_approve?).and_return(true)
     allow(MergeRequestApproverPresenter).to receive(:new).and_return(approver_presenter)
     assign(:project, project)
   end