Update default setting for unicorn worker_processes with new requirements
Unicorn workers now in general take more than 300MB, and the calculation we do for the workers vs Ram doesn't account for that. We should bump the calculation to use 400MB
Also the addition of gitaly-ruby has added another ~200MB load on the ram, so we should factor that in (by bumping up the 1GB we don't include in the calculation.)
cc\ @stanhu