website_event_booth_sale/views/event_booth_registration_templates.xml

<?xml version="1.0" encoding="UTF-8" ?>
<odoo><data>

    <template id="event_booth_registration_details" inherit_id="website_event_booth.event_booth_registration_details">
        <xpath expr="//button[hasclass('o_wbooth_registration_confirm')]//span" position="replace">
            <t t-if="has_payment_step">Go to Payment</t>
            <t t-else="">Book my Booth(s)</t>
        </xpath>
    </template>

</data></odoo>