add_filter('wpcf7_form_elements', function ($content) {
$content = preg_replace('/<(span).*?class="\s*(?:.*\s)?wpcf7-form-control-wrap(?:\s[^"]+)?\s*"[^\>]*>(.*)<\/\1>/i', '\2', $content);
return $content;
});
<span class="wpcf7-form-control wpcf7-acceptance">
<span class="wpcf7-list-item">
<input type="checkbox" name="our-policy" value="1" aria-invalid="false" class="form-check-input" id="our-policy">
</span>
</span>
$text = '<span class="wpcf7-form-control wpcf7-acceptance">
<span class="wpcf7-list-item">
<input type="checkbox" name="our-policy" value="1" aria-invalid="false" class="form-check-input" id="our-policy">
</span>
<span class="list-item">
<input type="checkbox" name="our-policy" value="1" aria-invalid="false" class="form-check-input" id="our-policy">
</span>
<span class="wpcf7-list-item">
<input type="checkbox" name="our-policy" value="1" aria-invalid="false" class="form-check-input" id="our-policy">
</span>
</span>';
$patterns = [
'~<span[^>]*wpcf7[^>]*>\s*(<input[^>]+>)\s*</span>~s',
'~<span[^>]*wpcf7[^>]*>(.+)</span>~s'
];
$text = preg_replace($patterns, '$1', $text);
echo $text;
/* Результат:
<input type="checkbox" name="our-policy" value="1" aria-invalid="false" class="form-check-input" id="our-policy">
<span class="list-item">
<input type="checkbox" name="our-policy" value="1" aria-invalid="false" class="form-check-input" id="our-policy">
</span>
<input type="checkbox" name="our-policy" value="1" aria-invalid="false" class="form-check-input" id="our-policy">
*/