Master fix qweb utf 8 encode rga

- Task: https://www.odoo.com/web?#id=9093&view_type=form&model=project.task
- Pad: https://pad.odoo.com/p/r.QlQTvBv6mCcMrK4B
That makes no sense, the function is apparently supposed to return UTF-8-encoded data, but this returns a unicode string which may fail to be encoded afterwards.