Remove unused view files.

app/views/projects/merge_requests/widget/open/_approve.html.haml

-%give-approval{ '@give-approval' => 'approveMergeRequest', ':approverNames' => 'approverNames', ':approvalsLeft' => 'approvalsLeft', ':moreApprovals' => 'moreApprovals', ':canApprove' => 'canApprove' }

app/views/projects/merge_requests/widget/open/_approvers.html.haml

-.mr-widget-footer.approved-by-users
-  %remove-approval{ '@remove-approval' => 'unapproveMergeRequest', ':approverNames' => 'approverNames', ':approvalsLeft' => 'approvalsLeft', ':moreApprovals' => 'moreApprovals', ':canApprove' => 'canApprove' }
-    %span{ slot: 'links-to-members'}
-      - @merge_request.approved_by_users.each do |user|
-        = link_to_member(@project, user, name: false, size: 24)