Since implementation of repartition lines on tax in accounting, the
amount on the tax is not always the effective amount to apply on price
of a product. You can have a tax with amount of 20% for example, and two
repartition lines of 100% and -100%, that will lead to have to apply 0%
on the tax.

So we are computing the effective amount on the tax by multiplying the
amount of tax by the sum of repartition lines factor.

closes odoo/odoo#36140

Signed-off-by: Laurent Smet <smetl@users.noreply.github.com>