Revert "XXX-zope4py3: zodbpickle: Dirty hack to have encoding sets to utf-8."

This reverts commit 31eaaec1.

This slows down business template by a factor of two and it seems we
don't need it. I'm experimenting with hacks in ppml.py but maybe just
creating the Unpickler with encoding='utf-8' in
product/ERP5Type/XMLExportImport/__init__.py:267 is enough ?