This reverts commit 31eaaec1a2bd8bc8648a686a83be989a9615a93e.

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 ?