go: Update our graphql-go dependency
Created by: ryanslade
To include this commit: https://github.com/sourcegraph/graphql-go/commit/8462b0b708c44d9a44eade8973be857b1a05029a
Created by: ryanslade
To include this commit: https://github.com/sourcegraph/graphql-go/commit/8462b0b708c44d9a44eade8973be857b1a05029a