[FIX] l10n_ae: Reverse charge with Vendor Bill

The reverse charge was counted twice in the VAT Return Summary Report

A reverse charge tax is a group of taxes with:
- Reverse Charge TVA +5%(Purchase)
- Reverse Charge TVA -5%(Purchase)

When buying a product P with a reverse charge tax on it.
The only tax that must appear in the VAT Return Summary Report is
the Reverse Charge TVA -5%(Purchase)

opw:2041877

closes odoo/odoo#35499

Signed-off-by: Simon Goffin (sig) <sig@openerp.com>