Use HTTPS to fetch App-cpanminus

[J0WI]

These should be updated to use HTTPS.
I'm sorry that I can't provide a PR myself, generate.pl was always messing with my local Git config.

docker-perl/generate.pl

Lines 85 to 88 in 0cb4fc3

 # sha256 taken from http://www.cpan.org/authors/id/M/MI/MIYAGAWA/CHECKSUMS 
 my %cpanm = ( 
   name   => "App-cpanminus-1.7044", 
   url    => "http://www.cpan.org/authors/id/M/MI/MIYAGAWA/App-cpanminus-1.7044.tar.gz", 

[Zak B. Elep]

Thanks @J0WI! I've already regenerated the Dockerfiles; they'll be updated in the Docker Hub on the next release.