Downgrade fatpacked CPAN::Meta

CPAN::Meta::Converter which is fatpacked by cpanm-1.7002 (@233c75b9d597b83cac7004e766154ce5f7086897)
requires version 1.33 of List::Util, however that is a not core module,
thus `cpanm` cannot work certainly on initial environment of Perl.

So downgrade CPAN::Meta to exclude dependency on List::Util.