It was accidentally removed in T318055: Collapsable suggestions box
We just need to add the following i18n strings to campaign_entry.html
"Are you sure you want to reject this suggestion?": {{ _('Are you sure you want to reject this suggestion?')|tojson }},
"Are you sure explanation for reject suggestion": {{ _('Only do this if you are sure the suggested tag does not appear in the image, or would be incorrect according to Wikimedia Commons guidelines. If several users reject the same suggestion, it will no longer be shown.')|tojson }}