docker/nginx: Align objstorage proxy_read_timeout value with production

As in production settings for the objstorage reverse proxy, set HTTP read
timeout to 1h in order to avoid 504 error (Gateway Time-out) when posting
a large amount of contents to the objects storage.

docker/conf/nginx.conf

@@ -97,6 +97,7 @@ http {
 
       rewrite ^/objstorage/(.*)$ /$1 break;
       proxy_pass $upstream;
+      proxy_read_timeout 3600s;
     }
     location /prometheus {
       set $upstream "http://prometheus:9090";