[FIX] account: Not enough account codes for created journals

When journals of type bank are created, default accounts are also
created, and an account code is automatically generated. However, the
number of possible automatic account codes is very limited, because only
100 different codes may be generated, and the error message "Cannot
generate an unused account code" is shown.

To solve the above, the number of possible account codes is raised up to
10,000 different possibilities.

closes odoo/odoo#31681

Signed-off-by: Quentin De Paoli (qdp) <qdp@openerp.com>