Change 'initiate' to 'initialize' in installation.rst (#9619)
Change 'initiate' to 'initialize' in installation.rst (#9619)

`Initiating Airflow Database` -> `Initializing Airflow Database`
cfei18/incubator-airflow,lyft/incubator-airflow,Acehaidrey/incubator-airflow,mistercrunch/airflow,bolkedebruin/airflow,Acehaidrey/incubator-airflow,cfei18/incubator-airflow,nathanielvarona/airflow,lyft/incubator-airflow,danielvdende/incubator-airflow,danielvdende/incubator-airflow,dhuang/incubator-airflow,dhuang/incubator-airflow,bolkedebruin/airflow,cfei18/incubator-airflow,danielvdende/incubator-airflow,cfei18/incubator-airflow,sekikn/incubator-airflow,airbnb/airflow,airbnb/airflow,apache/airflow,sekikn/incubator-airflow,bolkedebruin/airflow,nathanielvarona/airflow,sekikn/incubator-airflow,DinoCow/airflow,lyft/incubator-airflow,apache/incubator-airflow,mistercrunch/airflow,danielvdende/incubator-airflow,dhuang/incubator-airflow,mrkm4ntr/incubator-airflow,dhuang/incubator-airflow,Acehaidrey/incubator-airflow,danielvdende/incubator-airflow,mistercrunch/airflow,danielvdende/incubator-airflow,bolkedebruin/airflow,mrkm4ntr/incubator-airflow,DinoCow/airflow,mrkm4ntr/incubator-airflow,apache/airflow,nathanielvarona/airflow,apache/airflow,mrkm4ntr/incubator-airflow,mistercrunch/airflow,cfei18/incubator-airflow,lyft/incubator-airflow,airbnb/airflow,apache/incubator-airflow,nathanielvarona/airflow,nathanielvarona/airflow,nathanielvarona/airflow,DinoCow/airflow,sekikn/incubator-airflow,DinoCow/airflow,apache/airflow,Acehaidrey/incubator-airflow,airbnb/airflow,bolkedebruin/airflow,apache/incubator-airflow,Acehaidrey/incubator-airflow,cfei18/incubator-airflow,apache/incubator-airflow,apache/airflow,apache/airflow,Acehaidrey/incubator-airflow