Update ``README.md`` to point to Airflow 2.1.3 (#17793)
Update ``README.md`` to point to Airflow 2.1.3 (#17793)


apache/airflow,nathanielvarona/airflow,lyft/incubator-airflow,danielvdende/incubator-airflow,apache/airflow,apache/incubator-airflow,Acehaidrey/incubator-airflow,apache/airflow,nathanielvarona/airflow,danielvdende/incubator-airflow,danielvdende/incubator-airflow,bolkedebruin/airflow,apache/incubator-airflow,nathanielvarona/airflow,cfei18/incubator-airflow,Acehaidrey/incubator-airflow,danielvdende/incubator-airflow,cfei18/incubator-airflow,cfei18/incubator-airflow,mistercrunch/airflow,apache/incubator-airflow,bolkedebruin/airflow,Acehaidrey/incubator-airflow,apache/incubator-airflow,apache/airflow,nathanielvarona/airflow,Acehaidrey/incubator-airflow,cfei18/incubator-airflow,bolkedebruin/airflow,Acehaidrey/incubator-airflow,apache/airflow,bolkedebruin/airflow,mistercrunch/airflow,mistercrunch/airflow,danielvdende/incubator-airflow,danielvdende/incubator-airflow,mistercrunch/airflow,cfei18/incubator-airflow,lyft/incubator-airflow,Acehaidrey/incubator-airflow,lyft/incubator-airflow,bolkedebruin/airflow,apache/airflow,nathanielvarona/airflow,cfei18/incubator-airflow,nathanielvarona/airflow,lyft/incubator-airflow