Fix broken master on Ruby 2.1

Signed-off-by: Rémy Coutable <remy@rymai.me>

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

-%approvals-body{ ':user-can-approve' => 'approvals.user_can_approve', ':user-has-approved' => 'approvals.user_has_approved', ':approved-by' => 'approvals.approved_by', ':approvals-left':'approvals.approvals_left', ':suggested-approvers' => 'approvals.suggested_approvers' }
+%approvals-body{ ':user-can-approve' => 'approvals.user_can_approve', ':user-has-approved' => 'approvals.user_has_approved', ':approved-by' => 'approvals.approved_by', ':approvals-left' => 'approvals.approvals_left', ':suggested-approvers' => 'approvals.suggested_approvers' }