[FIX] web: Allow users to enable list view with group_by_no_leaf

[abz-odoo]

• Go to accounting/Report/Invoices Analysis
• Open studio
• enable list view
• empty view

This code bellow compute count_field as __count because group_by_no_leaf is in the context.

But in the basic_model we don't consider this case.

https://github.com/odoo/odoo/blob/5797fd80a63309269f15bcbe4948d4429a53eec2/odoo/models.py#L2293-L2297

opw-2980923

[abz-odoo]

@fw-bot up to saas-15.3

[robodoo]

[fw-bot]

Forward-porting to 'saas-15.3'.

[abz-odoo]

16.0 -> master pr: https://github.com/odoo/odoo/pull/100872