Replace deprecated decorator (#13443)
Replace deprecated decorator (#13443)

`abc.abstractproperty` is deprecated since Python 3.3. Instead we should use `@property` with `abc.abstractmethod`.

Docs: https://docs.python.org/3.6/library/abc.html#abc.abstractproperty
Acehaidrey/incubator-airflow,dhuang/incubator-airflow,nathanielvarona/airflow,apache/airflow,apache/airflow,mistercrunch/airflow,danielvdende/incubator-airflow,Acehaidrey/incubator-airflow,lyft/incubator-airflow,danielvdende/incubator-airflow,nathanielvarona/airflow,lyft/incubator-airflow,apache/incubator-airflow,cfei18/incubator-airflow,apache/incubator-airflow,nathanielvarona/airflow,apache/airflow,cfei18/incubator-airflow,nathanielvarona/airflow,danielvdende/incubator-airflow,Acehaidrey/incubator-airflow,sekikn/incubator-airflow,cfei18/incubator-airflow,dhuang/incubator-airflow,apache/airflow,bolkedebruin/airflow,cfei18/incubator-airflow,danielvdende/incubator-airflow,Acehaidrey/incubator-airflow,mistercrunch/airflow,nathanielvarona/airflow,sekikn/incubator-airflow,dhuang/incubator-airflow,dhuang/incubator-airflow,apache/incubator-airflow,apache/incubator-airflow,mistercrunch/airflow,apache/airflow,bolkedebruin/airflow,Acehaidrey/incubator-airflow,lyft/incubator-airflow,lyft/incubator-airflow,bolkedebruin/airflow,cfei18/incubator-airflow,danielvdende/incubator-airflow,bolkedebruin/airflow,danielvdende/incubator-airflow,cfei18/incubator-airflow,mistercrunch/airflow,Acehaidrey/incubator-airflow,bolkedebruin/airflow,nathanielvarona/airflow,sekikn/incubator-airflow,apache/airflow,sekikn/incubator-airflow