Fix docs on creating CustomOperator (#8678)
Fix docs on creating CustomOperator (#8678)


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