fixup! erp5_interface_post: sent Mail Message now display their post equivalent as preview

bt5/erp5_interface_post/SkinTemplateItem/portal_skins/erp5_interface_post/Base_getFirstPartFromMultipartMessage.py

@@ -9,7 +9,7 @@ import email
 
 message = email.message_from_string(data)
 
-payload = message.get_payload(decode=True)
+payload = message.get_payload()
 
 while isinstance(payload, list):
   payload = payload[0].get_payload(decode=True)