tests: remove SKIP_CLOUDFLARE_CHECK env variable.

This was a hack to deal with the Cloudflare check sometimes being slow
or timing out during tests. The call to https://api.cloudflare.com/client/v4/ips
could hang if there were IPv6 connectivity problems. If this happens, make
sure that IPv6 is configured properly and that `curl -v --http1.1 -6 https://api.cloudflare.com/client/v4/ips`
works.

db/populate.rb

@@ -95,8 +95,6 @@ CurrentUser.user = User.admins.first
 CurrentUser.ip_addr = "127.0.0.1"
 
 if Upload.count == 0
-  ENV["SKIP_CLOUDFLARE_CHECK"] = "true"
-
   puts "Creating uploads"
   1.upto(50) do |i|
     color1 = rand(4096).to_s(16)