pos/pos_remove_pos_category/views/pos_view.xml

<?xml version="1.0" encoding="utf-8"?>
<odoo>
    <record id="product_template_form_view" model="ir.ui.view">
        <field name="name">hide.pos_categ_id.product.template.form</field>
        <field name="model">product.template</field>
        <field name="inherit_id" ref="point_of_sale.product_template_form_view"/>
        <field name="arch" type="xml">
            <field name="pos_categ_id" position="attributes">
                <attribute name="invisible">1</attribute>
            </field>
        </field>
    </record>
    <record id="point_of_sale.product_pos_category_action" model="ir.actions.act_window">
        <field name="res_model">product.category</field>
    </record>
</odoo>