[FIX] packaging: add num2words debian depends

The num2words Debian package exists in Debian Buster [0] and Ubuntu
Focal [1].

[0]: https://packages.debian.org/buster/python3-num2words
[1]: https://packages.ubuntu.com/focal/python3-num2words



closes odoo/odoo#70666

X-original-commit: f882512f
Signed-off-by: Christophe Monniez (moc) <moc@odoo.com>