[FIX] l10n_at: tax template repartition lines

1) The aim of this commit is to make the tax template more consistent with
the instanciated tax.
Indeed a tax wouldn't pass the constrains if it hadn't all its
repartition line.

2) Make the refund consistent with the rest of the taxes.

closes odoo/odoo#132542

Task-id: None
X-original-commit: c8603a9e
Signed-off-by: Florian Gilbert (flg) <flg@odoo.com>