Remove variable defaults

These are not set whenever a merged compose file is used

docker-compose.production.yml

@@ -9,6 +9,9 @@ services:
     depends_on:
       django:
         condition: service_healthy
+    ports:
+      - "${NGINX_HTTP_PORT:-80}:80"
+      - "${NGINX_HTTPS_PORT:-443}:443"
     volumes:
       - ./config/nginx/conf.d:/etc/nginx/conf.d
       - logs:/var/log/nginx