[FIX] point_of_sale: pos is launched with all companies

- Activate multicompany
- In the company switcher select all company
- Launch a pos session
--> Issue all rpc request are make in all companies (len(self.env.companies) != 1). It create some error with taxes, fiscale position, ...

closes odoo/odoo#76393

Signed-off-by: pimodoo <pimodoo@users.noreply.github.com>