doc: add a go/golang entry to the FAQ

It's worth clarifying that the language is called "Go".

Fixes #27616.

Change-Id: Ie4a9cb5e7e6afa437c60e06914125ef7490f27d0
Reviewed-on: https://go-review.googlesource.com/135517


Reviewed-by: Ian Lance Taylor <iant@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>