Revert "FIX: Set the Host header in the nginx.conf upstream block"

This reverts commit d8a363b.

Support for this was removed in nginx - I was unintentionally testing on an old version

Author: Supermathie

templates/web.template.yml

@@ -146,7 +146,6 @@ run:
       filename: "/etc/nginx/conf.d/discourse.conf"
       from: /upstream[^\}]+\}/m
       to: "upstream discourse {
-        set_header Host $http_host;
         server 127.0.0.1:3000;
       }"