erp5_officejs_connector: -revert- restoring content_type field on WebPage_viewAsJio

- this fixes a unit test on code mirror app
- WIP: all changes in connector must be discarded/reverted

bt5/erp5_officejs_connector/SkinTemplateItem/portal_skins/erp5_officejs_jio_connector/WebPage_viewAsJio.xml

@@ -79,6 +79,7 @@
                         <string>my_title</string>
                         <string>my_reference</string>
                         <string>your_modification_date</string>
+                        <string>my_content_type</string>
                       </list>
                     </value>
                 </item>