add_action('wp_ajax_acf_repeater_show_more', 'reviews_show_more');
то action в js должен быть acf_repeater_show_more, а не reviews_show_more $ch=curl_init();
curl_setopt($ch, CURLOPT_URL,
'https://api.telegram.org/bot'.$token.'/sendMessage');
curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
curl_setopt($ch, CURLOPT_HEADER, false);
curl_setopt($ch, CURLOPT_SSL_VERIFYPEER, false);
curl_setopt($ch, CURLOPT_POST, true);
curl_setopt($ch, CURLOPT_POSTFIELDS,
'chat_id='.$chat_id.'&text='.urlencode($text).'&parse_mode=html');
curl_setopt($ch, CURLOPT_CONNECTTIMEOUT, 10);
$result=curl_exec($ch);
curl_close($ch);