Update README to remove Py 3.8 limitation for Master (#9451)
Update README to remove Py 3.8 limitation for Master (#9451)


DinoCow/airflow,lyft/incubator-airflow,cfei18/incubator-airflow,Acehaidrey/incubator-airflow,dhuang/incubator-airflow,apache/airflow,Acehaidrey/incubator-airflow,Acehaidrey/incubator-airflow,mrkm4ntr/incubator-airflow,nathanielvarona/airflow,bolkedebruin/airflow,dhuang/incubator-airflow,airbnb/airflow,mrkm4ntr/incubator-airflow,danielvdende/incubator-airflow,apache/airflow,airbnb/airflow,sekikn/incubator-airflow,mrkm4ntr/incubator-airflow,apache/airflow,mistercrunch/airflow,cfei18/incubator-airflow,danielvdende/incubator-airflow,DinoCow/airflow,bolkedebruin/airflow,lyft/incubator-airflow,apache/incubator-airflow,DinoCow/airflow,bolkedebruin/airflow,danielvdende/incubator-airflow,cfei18/incubator-airflow,airbnb/airflow,apache/airflow,Acehaidrey/incubator-airflow,lyft/incubator-airflow,cfei18/incubator-airflow,bolkedebruin/airflow,nathanielvarona/airflow,apache/incubator-airflow,apache/airflow,cfei18/incubator-airflow,airbnb/airflow,bolkedebruin/airflow,apache/incubator-airflow,danielvdende/incubator-airflow,danielvdende/incubator-airflow,mistercrunch/airflow,lyft/incubator-airflow,sekikn/incubator-airflow,Acehaidrey/incubator-airflow,dhuang/incubator-airflow,sekikn/incubator-airflow,dhuang/incubator-airflow,nathanielvarona/airflow,Acehaidrey/incubator-airflow,mistercrunch/airflow,cfei18/incubator-airflow,nathanielvarona/airflow,apache/airflow,apache/incubator-airflow,nathanielvarona/airflow,sekikn/incubator-airflow,mistercrunch/airflow,DinoCow/airflow,mrkm4ntr/incubator-airflow,nathanielvarona/airflow,danielvdende/incubator-airflow