[AIRFLOW-5561] Relax httplib2 version required for gcp extra (#6194)
[AIRFLOW-5561] Relax httplib2 version required for gcp extra (#6194)

As part of [AIRFLOW-3971] a minor version range dependency was
introduced that means that only older versions of httplib2 can
be used.

I'm relaxing this dependency as I tested with the latest 0.13.1
and it works correctly
spektom/incubator-airflow,apache/airflow,mtagle/airflow,wooga/airflow,danielvdende/incubator-airflow,danielvdende/incubator-airflow,mtagle/airflow,Acehaidrey/incubator-airflow,DinoCow/airflow,nathanielvarona/airflow,danielvdende/incubator-airflow,mtagle/airflow,DinoCow/airflow,nathanielvarona/airflow,apache/airflow,bolkedebruin/airflow,cfei18/incubator-airflow,sekikn/incubator-airflow,Acehaidrey/incubator-airflow,apache/airflow,apache/airflow,apache/airflow,nathanielvarona/airflow,apache/incubator-airflow,bolkedebruin/airflow,bolkedebruin/airflow,spektom/incubator-airflow,mrkm4ntr/incubator-airflow,sekikn/incubator-airflow,lyft/incubator-airflow,cfei18/incubator-airflow,lyft/incubator-airflow,dhuang/incubator-airflow,mistercrunch/airflow,Acehaidrey/incubator-airflow,Acehaidrey/incubator-airflow,airbnb/airflow,mrkm4ntr/incubator-airflow,nathanielvarona/airflow,cfei18/incubator-airflow,apache/incubator-airflow,lyft/incubator-airflow,wooga/airflow,bolkedebruin/airflow,Acehaidrey/incubator-airflow,apache/incubator-airflow,Fokko/incubator-airflow,airbnb/airflow,airbnb/airflow,wileeam/airflow,dhuang/incubator-airflow,lyft/incubator-airflow,wileeam/airflow,wooga/airflow,wooga/airflow,DinoCow/airflow,mistercrunch/airflow,danielvdende/incubator-airflow,cfei18/incubator-airflow,danielvdende/incubator-airflow,dhuang/incubator-airflow,airbnb/airflow,cfei18/incubator-airflow,nathanielvarona/airflow,bolkedebruin/airflow,mrkm4ntr/incubator-airflow,spektom/incubator-airflow,sekikn/incubator-airflow,mrkm4ntr/incubator-airflow,Fokko/incubator-airflow,nathanielvarona/airflow,wileeam/airflow,Acehaidrey/incubator-airflow,danielvdende/incubator-airflow,spektom/incubator-airflow,mistercrunch/airflow,mtagle/airflow,dhuang/incubator-airflow,mistercrunch/airflow,cfei18/incubator-airflow,apache/airflow,sekikn/incubator-airflow,Fokko/incubator-airflow,Fokko/incubator-airflow,DinoCow/airflow,wileeam/airflow,apache/incubator-airflow