When the user submits a form, a lead will be created but the language
won't be the one selected by the user.

To reproduce the error:
(Enable debug mode)
1. Settings > Translations > Languages
2. Activate another language L_other
3. On website, add a form:
    - Action: Create an Opportunity
4. Add an existing field: "Language"
5. Submit the form
    - Language must be L_other
6. Consult the new lead

Error: The language is not the selected one.

OPW-2486276

closes odoo/odoo#69941

Signed-off-by: Adrien Widart <adwid@users.noreply.github.com>