before this commit, the lots info shown in the products were always computed, no matter if they were printed or
not.

after this commit, the lot info only is computed when is actually used and will be printed: that is when the user has the
stock_account.group_lot_on_invoice group.

closes odoo/odoo#110642

Signed-off-by: William Henrotin (whe) <whe@odoo.com>