doc: Fix Telegram invite group link (#1284)

Author: melroy89

README.md

@@ -126,4 +126,4 @@ Copyright © 2019 Yago
 [contributors]:https://github.com/yagop/node-telegram-bot-api/graphs/contributors
 [experimental]:https://github.com/yagop/node-telegram-bot-api/tree/master/doc/experimental.md
 [tg-channel]:https://telegram.me/node_telegram_bot_api
-[tg-group]:https://t.me/+nc3A9Hs1S81mYzdk
+[tg-group]:https://t.me/+UTbprHdcw0JdZdbL