Redirect HTTP -> HTTPS about zimfarm

[automactic]

I tested on safari and Firefox. It already does the redirection. No fix is needed.

@kelson42 Could you please test if the redirection happens for you.

[kelson42]

@automactic

Works fine now:

$ curl -I http://farm.openzim.org
HTTP/1.1 301 Moved Permanently
Server: nginx/1.15.6
Date: Wed, 26 Dec 2018 12:17:06 GMT
Content-Type: text/html
Content-Length: 169
Connection: keep-alive
Location: https://farm.openzim.org/