[FIX] account: reconcilation partial amount nice locale

If you reconcile for example a bank statement of 200,00€ with a
customer invoice of 300,00€, you get a pen icon next to the 300,00€
and if you click on it you have an editing cell with:

200.00

But if you validate this, this will be parse in the current language
number formatting so if you have . as thousands separator, this number
will become 20000 which is not expected (higher than original invoice).

With this changeset, we display the number in the current lang format.

note: with this fix, number of decimals can be different than 2

opw-2150396
closes #41410

closes odoo/odoo#41431

X-original-commit: 0fa0acca963075176bd8195ec66581653940ca7f
Signed-off-by: Nicolas Lempereur (nle) <nle@odoo.com>