fix map is not allowed in server context

The map directive is only allowed in the http context.
See https://nginx.org/en/docs/http/ngx_http_map_module.html

backend/templates/_location.conf

@@ -1,4 +1,3 @@
-  {% include "_hsts_map.conf" %}
 
   location {{ path }} {
     proxy_set_header Host $host;