{% if form_show_errors and field.errors %}
    {% for error in field.errors %}
        <p id="error_{{ forloop.counter }}_{{ field.auto_id }}" class="form-control-feedback"><strong>{{ error }}</strong></p>
    {% endfor %}
{% endif %}

{% if form_show_errors and field.errors %}
    {% for error in field.errors %}
        <p id="error_{{ forloop.counter }}_{{ field.auto_id }}" class="invalid-feedback"><strong>{{ error }}</strong></p>
    {% endfor %}
{% endif %}

Update field error template classes to 'invalid-feedback'
Update field error template classes to 'invalid-feedback'