`_render('<h1> quick & flupke </h1>') `=>` '<h1> quick & flupke </h1>'`
what cannot be parsed in xml after.
Before this commit, if you try to install a page that contains a '&' via
the configurator, you had a traceback:
xmlParseEntityRef: no name, line 1, column 13
closes odoo/odoo#73509
Signed-off-by: Jérémy Kersten (jke) <jke@openerp.com>