If this is a standard Docker install, you’ll also need to enter the app first.
cd /var/discourse
./launcher enter app
Assuming that succeeds, you can print line 46 of the config file with sed:
sed -n '46p' /etc/nginx/conf.d/discourse.conf
With the same templates as you and no specific modifications to that config file, I see this:
return 301 https://discourse.softpress.com$request_uri;