Hi there 👋

I was playing with the **TelegramOperator** and stumbled upon a bug with the `text` field. It is supposed to be a template field but in reality the instance of the **TelegramOperator** does not have this attribute thus every time I try to execute code I get the error:

> AttributeError: 'TelegramOperator' object has no attribute 'text'

```python
TelegramOperator(
        task_id='send_message_telegram',
        telegram_conn_id='telegram_conn_id',
        text='Hello from Airflow!'
    )
```
tests/providers/telegram/operators/test_telegram.py
with pytest.raises(airflow.exceptions.AirflowException) as ctx:
            TelegramOperator(task_id="telegram", telegram_conn_id=None)
        assert "No valid Telegram connection id supplied." == str(ctx.value)
    @mock.patch('airflow.providers.telegram.operators.telegram.TelegramHook')
    def test_should_throw_exception_if_telegram_hook_throws_any_exception(self, mock_telegram_hook):
        def side_effect(*args, **kwargs):
            raise telegram.error.TelegramError("cosmic rays caused bit flips")
        mock_telegram_hook.return_value = mock.Mock()
        mock_telegram_hook.return_value.send_message.side_effect = side_effect
        with pytest.raises(telegram.error.TelegramError) as ctx:
            hook = TelegramOperator(
                telegram_conn_id='telegram_default',
                task_id='telegram',
                text="some non empty text",
            )
            hook.execute()
        assert "cosmic rays caused bit flips" == str(ctx.value)
    @mock.patch('airflow.providers.telegram.operators.telegram.TelegramHook')
    def test_should_forward_all_args_to_telegram(self, mock_telegram_hook):