pos/pos_remove_pos_category/point_of_sale_view.xml

<?xml version="1.0" encoding="utf-8"?>
<openerp>
    <data>
        <record id="product_template_form_view" model="ir.ui.view">
            <field name="name">product.template.form.inherit</field>
            <field name="model">product.template</field>
            <field name="inherit_id" ref="product.product_template_form_view"/>
            <field name="priority" eval="100"/>
            <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>
    </data>
</openerp>