Fix Commands to install Airflow in docker/install_airflow.sh (#14099)
Fix Commands to install Airflow in docker/install_airflow.sh (#14099)

It was trying to run the following command and failing

```
pip install apache-airflow[amazon,google]2.0.0rc2
```
bolkedebruin/airflow,Acehaidrey/incubator-airflow,lyft/incubator-airflow,Acehaidrey/incubator-airflow,danielvdende/incubator-airflow,cfei18/incubator-airflow,danielvdende/incubator-airflow,apache/incubator-airflow,danielvdende/incubator-airflow,Acehaidrey/incubator-airflow,dhuang/incubator-airflow,lyft/incubator-airflow,mistercrunch/airflow,sekikn/incubator-airflow,apache/incubator-airflow,apache/airflow,sekikn/incubator-airflow,apache/airflow,nathanielvarona/airflow,cfei18/incubator-airflow,cfei18/incubator-airflow,bolkedebruin/airflow,mistercrunch/airflow,sekikn/incubator-airflow,nathanielvarona/airflow,sekikn/incubator-airflow,dhuang/incubator-airflow,cfei18/incubator-airflow,cfei18/incubator-airflow,apache/airflow,dhuang/incubator-airflow,nathanielvarona/airflow,nathanielvarona/airflow,mistercrunch/airflow,apache/airflow,mistercrunch/airflow,Acehaidrey/incubator-airflow,danielvdende/incubator-airflow,apache/airflow,danielvdende/incubator-airflow,apache/incubator-airflow,bolkedebruin/airflow,lyft/incubator-airflow,apache/airflow,apache/incubator-airflow,cfei18/incubator-airflow,dhuang/incubator-airflow,nathanielvarona/airflow,Acehaidrey/incubator-airflow,lyft/incubator-airflow,nathanielvarona/airflow,Acehaidrey/incubator-airflow,bolkedebruin/airflow,danielvdende/incubator-airflow,bolkedebruin/airflow