Fix http_raw_prepend/append indentation

[matejzero]

Pull Request (PR) description

http_raw_prepend and http_raw_append have wrong indentation. Example with current template:

  ssl_stapling_verify       off;

    real_ip_header X-Forwarded-For;
    set_real_ip_from 1.2.3.4;

  include /etc/nginx/conf.d/*.conf;

This MR removes 2 extra spaces.

[kenyon]

Since this would cause a restart of the nginx service, IMO we should wait to merge this until we do a major release.

[matejzero]

I can live with that, I think it's only a cosmetic fix.