[FIX] l10n_fr_fec: no cash basis compute

Before this, there was a computation of cash basis moves for each reconciliation
done during FEC import and it can slow down a lot the import for nothing since
no taxes will be in the imported entries so no cash basis will result from
reconciliation.

Now, the cash basis moves computation is skipped to improve the performance.

Here are the stats of reconciliation time on fresh database using a FEC file
of ~76000 amls including ~15000 reconciled.

V15 without fix => 8 min 15 s
V15 with fix => 5 min 27 s

V16 without fix => 9 min 36 s
V16 with fix => 1 min 33 s

opw-3274391

closes odoo/odoo#131510

Related: odoo/enterprise#45603
Signed-off-by: Laurent Smet (las) <las@odoo.com>