Update slack invite link (#3275)
Update slack invite link (#3275)

The old one was expired.

Signed-off-by: Sue Ann Hong <427e6e0c205e7d714dba697d647615bba570bb11@databricks.com>
mlflow/mlflow,mlflow/mlflow,mlflow/mlflow,mlflow/mlflow,mlflow/mlflow,mlflow/mlflow,mlflow/mlflow