erp5_run_my_doc: set missing http cache for css file

bt5/erp5_run_my_doc/SkinTemplateItem/portal_skins/erp5_run_my_doc/test_page_report.css.xml

@@ -6,6 +6,10 @@
     </pickle>
     <pickle>
       <dictionary>
+        <item>
+            <key> <string>_Cacheable__manager_id</string> </key>
+            <value> <string>must_revalidate_http_cache</string> </value>
+        </item>
         <item>
             <key> <string>__name__</string> </key>
             <value> <string>test_page_report.css</string> </value>