Fixed image separator for Github Package registry image (#13825)
Fixed image separator for Github Package registry image (#13825)

The #13726 introduced possibility of using Github Container
Registry, but for bulding from Package Registry there was a
mistake - only visible after merging - that introduced
failed master (naming of build image contained / rather than -)

This PR fixes it.
apache/airflow,nathanielvarona/airflow,dhuang/incubator-airflow,Acehaidrey/incubator-airflow,apache/incubator-airflow,nathanielvarona/airflow,bolkedebruin/airflow,Acehaidrey/incubator-airflow,apache/incubator-airflow,cfei18/incubator-airflow,danielvdende/incubator-airflow,lyft/incubator-airflow,cfei18/incubator-airflow,apache/airflow,cfei18/incubator-airflow,nathanielvarona/airflow,mistercrunch/airflow,bolkedebruin/airflow,apache/airflow,dhuang/incubator-airflow,apache/airflow,danielvdende/incubator-airflow,nathanielvarona/airflow,sekikn/incubator-airflow,sekikn/incubator-airflow,apache/airflow,sekikn/incubator-airflow,lyft/incubator-airflow,bolkedebruin/airflow,apache/incubator-airflow,apache/incubator-airflow,bolkedebruin/airflow,nathanielvarona/airflow,Acehaidrey/incubator-airflow,cfei18/incubator-airflow,sekikn/incubator-airflow,nathanielvarona/airflow,danielvdende/incubator-airflow,dhuang/incubator-airflow,lyft/incubator-airflow,danielvdende/incubator-airflow,mistercrunch/airflow,danielvdende/incubator-airflow,Acehaidrey/incubator-airflow,Acehaidrey/incubator-airflow,Acehaidrey/incubator-airflow,mistercrunch/airflow,mistercrunch/airflow,cfei18/incubator-airflow,bolkedebruin/airflow,cfei18/incubator-airflow,danielvdende/incubator-airflow,apache/airflow,dhuang/incubator-airflow,lyft/incubator-airflow