Symfony 4.4+ Remove Multiple Choice Option

ChoiceTypeExtension.php

<?php

/**
 * ChoiceType "preferred_choice_twice" Extension
 *
 * @author Ramazan APAYDIN <apaydin541@gmail.com>
 */
class ChoiceTypeExtension extends AbstractTypeExtension
{
    public function buildView(FormView $view, FormInterface $form, array $options)
    {
        parent::buildView($view, $form, $options);

        if (is_array($view->vars['preferred_choices'])) {
            foreach ($view->vars['preferred_choices'] as $index => $choices) {
                unset($view->vars['choices'][$index]);
            }
        }
    }

    public static function getExtendedTypes(): iterable
    {
        return [ChoiceType::class];
    }
}

form_div_layout.html.twig

{%- block choice_widget_collapsed -%}
    {%- if required and placeholder is none and not placeholder_in_choices and not multiple and (attr.size is not defined or attr.size <= 1) -%}
        {% set required = false %}
    {%- endif -%}
    <select {{ block('widget_attributes') }}{% if multiple %} multiple="multiple"{% endif %}>
        {%- if placeholder is not none -%}
            <option value=""{% if required and value is empty %} selected="selected"{% endif %}>{{ placeholder != '' ? (translation_domain is same as(false) ? placeholder : placeholder|trans({}, translation_domain)) }}</option>
        {%- endif -%}

        {%- if preferred_choices|length > 0 -%}
            {% set options = preferred_choices %}
            {% set render_preferred_choices = false %}
            {{- block('choice_widget_options') -}}
            {%- if choices|length > 0 and separator is not none -%}
                <option disabled="disabled">{{ separator }}</option>
            {%- endif -%}
        {%- endif -%}

        {%- set options = choices -%}
        {%- set render_preferred_choices = false -%}
        {{- block('choice_widget_options') -}}
    </select>
{%- endblock choice_widget_collapsed -%}