web/web_favicon/views/res_company.xml

<?xml version="1.0" encoding="UTF-8"?>
<odoo>
    <record id="view_company_form" model="ir.ui.view">
        <field name="model">res.company</field>
        <field name="inherit_id" ref="base.view_company_form" />
        <field name="arch" type="xml">
            <notebook position="inside">
                <page string="Web Favicon" name="favicon" groups="base.group_system">
                    <group string="Favicon" name="favicon">
                        <field name="favicon_backend" widget="image" />
                        <field name="favicon_backend_mimetype" attrs="{'required': [('favicon_backend', '!=', False)]}" />
                    </group>
                </page>
            </notebook>
        </field>
    </record>
</odoo>