base: Image should not acquire local roles

All top level documents are not supposed to acquire local roles
https://www.erp5.com/erp5-Guideline.Unset.Acquire.Local.Roles.On.Document.Portal.Type.Configuration.If.Applicable

I believe this comes from the time where we were using images as
sub-documents of products or persons. We now use embedded files for
these cases, so no need to have an exception here.

bt5/erp5_base/PortalTypeTemplateItem/portal_types/Image.xml

@@ -27,7 +27,7 @@
         </item>
         <item>
             <key> <string>acquire_local_roles</string> </key>
-            <value> <int>1</int> </value>
+            <value> <int>0</int> </value>
         </item>
         <item>
             <key> <string>content_icon</string> </key>