I cannot import project (I cannot add "client_max_body_size" to nginx in the omnibus package)

Pre-note: First I introduced this bug in https://gitlab.com/gitlab-org/gitlab-ce/issues/1508 (now I deleted it to avoid duplication of information).

selfhosted gitlab-ce in debian9 with omnibus in the latest stable version.

I'm trying to import an exported project from gitlab.com but I get 413 Request Entity Too Large

The project has 3 MB in the tar.gz

/etc/gitlab/gitlab.rb looks like:

#nginx['enable'] = true
#nginx['client_max_body_size'] = '250m'
nginx['client_max_body_size'] = '100m'
#nginx['redirect_http_to_https'] = false
#nginx['redirect_http_to_https_port'] = 80

I also tried enabling the rest of these lines but there is no different effect.

This is the admin page:

saved in admin preferences and performed gitlab-ctl reconfigure