lib/model: Clarify master terminology (fixes #2679)

GitHub-Pull-Request: https://github.com/syncthing/syncthing/pull/3793

gui/default/index.html

@@ -354,7 +354,7 @@
                     <tr ng-if="folder.type != 'readwrite'">
                       <th><span class="fa fa-fw fa-lock"></span>&nbsp;<span translate>Folder Type</span></th>
                       <td class="text-right">
-                        <span ng-if="folder.type == 'readonly'" translate>Master</span>
+                        <span ng-if="folder.type == 'readonly'" translate>Send Only</span>
                         <span ng-if="folder.type != 'readonly'">{{ folder.type.charAt(0).toUpperCase() + folder.type.slice(1) }}</span>
                       </td>
                     </tr>