You can use form theming. As described here, add a theme file:
{# src/AppBundle/Resources/views/Orders/theme.html.twig #}
{% extends 'form_div_layout.html.twig' %}
and reference it from the template where the form is rendered:
{# src/AppBundle/Resources/views/Orders/show.html.twig #}
{% form_theme form 'AppBundle:Orders:theme.html.twig' %}
{{ form_start(form) }}
{{ form_widget(form) }}
<input type="submit" value="Pay € {{ order.amount }}" />
{{ form_end(form) }}
Then, add the "jms_choose_payment_method_data_paypal_express_checkout" label field with no content in the theme file:
{% block _jms_choose_payment_method_data_paypal_express_checkout_label %}
{% endblock %}
And you're done.