erp5_officejs: fix synchronization spreadsheet gadget

bt5/erp5_officejs/SkinTemplateItem/portal_skins/erp5_officejs_theme/OOoDocument_viewAsJio/my_modification_date.xml

@@ -279,7 +279,7 @@
       <dictionary>
         <item>
             <key> <string>_text</string> </key>
-            <value> <string>python: here.getModificationDate().strftime(\'%d/%m/%Y\')</string> </value>
+            <value> <string>python: here.getModificationDate().HTML4()</string> </value>
         </item>
       </dictionary>
     </pickle>

[Cédric Le Ninivin]

Could you also please update the name of the field to use prefix your_ like in 8ed0408b . This avoid the property to be included by edit. It is a nice way to provide extra information with jIO without the risk to modify the data.