Put possibly replaces sections in the right columns. Fixes ietf-tools#1802. Commit ready for merge.

 - Legacy-Id: 10414

Author: rjsparks

ietf/templates/doc/document_draft.html

@@ -104,6 +104,7 @@
       {% if can_view_possibly_replaces %}
           {% if possibly_replaces %}
             <tr>
+              <th></th>
               <th>Possibly Replaces</th>
               <td class="edit">
                 {% if can_edit_replaces %}
@@ -118,6 +119,7 @@
 
           {% if possibly_replaced_by %}
             <tr>
+              <th></th>
               <th>Possibly Replaced By</th>
               <td class="edit">
                 {% if can_edit_replaces %}