Refresh docs to align with new name for component

[jjtswan]

Sounds like we're switching to either FHIR-info-gateway or maybe just FHIR-gateway. In which case, we should be updating various parts of the docs & diagrams in here, like this on here:

https://github.com/google/fhir-access-proxy/

May need to update package / repo names, etc.

This can wait for a fast follow.

[bashir2]

I believe @williamito is creating new images with "FHIR Gateway" (thanks).

[bashir2]

Actually the names in the new pictures might be "Access Gateway" (which is fine); @williamito can correct me.

[williamito]

I was only planning to extract the images from the doc you provided, which do use "Access Gateway".