user name changes: remove unused reason, status fields.

Remove all infrastructure around approving or rejecting user name
changes. Name changes haven't been moderated for several years.

* Remove status, approver_id, change_reason, and rejection_reason fields.
* Remove approve and reject controller actions.

app/views/user_name_change_requests/index.html.erb

@@ -6,9 +6,8 @@
       <thead>
         <tr>
           <th>User</th>
-          <th>Request</th>
-          <th>Reason</th>
-          <th>Status</th>
+          <th>Old Name</th>
+          <th>New Name</th>
           <th>Date</th>
           <th></th>
         </tr>
@@ -17,23 +16,8 @@
         <% @change_requests.each do |change_request| %>
           <tr>
             <td><%= link_to_user change_request.user %></td>
-            <td>
-              <strong><%= change_request.original_name %></strong> ->
-              <strong><%= change_request.desired_name %></strong>
-            </td>
-            <td>
-              <% if CurrentUser.is_admin? || CurrentUser.user == change_request.user %>
-                <%= change_request.change_reason %>
-              <% end %>
-            </td>
-            <td>
-              <%= change_request.status %>
-              <% if change_request.approved? %>
-                by <%= link_to_user change_request.approver %>
-              <% elsif change_request.rejected? %>
-                for reason: <%= link_to change_request.rejection_reason %>
-              <% end %>
-            </td>
+            <td><%= change_request.original_name %></td>
+            <td><%= change_request.desired_name %></td>
             <td><%= compact_time change_request.created_at %></td>
             <td><%= link_to "view", user_name_change_request_path(change_request) %></td>
           </tr>