fix(docker): clear X-Forwarded-Proto entirely

It's passed through from the edge reverse proxy, so setting it again is
redundant.

docker/nginx/nginx.conf

@@ -28,7 +28,6 @@ server {
 
         proxy_pass http://shipper;
         proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
-        proxy_set_header X-Forwarded-Proto $http_x_forwarded_proto;
         proxy_set_header Host $host;
         proxy_redirect off;
     }