[FIX] account: Fix broken matching rules tests depending of the date

Fix of 9af5516e:

Since we are now in 2020, the demo-data are now created in 2020 and then, the
sequence number are not the same when executing the tests:
E.g. INV/2019/0001 instead of INV/2019/0005.

After this commit, this test no longer depends of demo data.

closes odoo/odoo#43397

Signed-off-by: oco-odoo <oco-odoo@users.noreply.github.com>