[IMP] base_vat: Allow T as country code for JP companies Tax ID

Description of the issue/feature this commit addresses:

As of the first October 2023, some Japanese companies will start using "T" as
country code in their Tax ID. The current vat check only allows the country
code to be used in the Tax ID which means that "T" is refused.

Desired behavior after the commit is merged :

This commit makes it possible for Japanese companies to use "T" as a
country code in their Tax ID.

task-3515786

closes odoo/odoo#136146

Signed-off-by: Quentin De Paoli <qdp@odoo.com>