community/perl-datetime-format-natural: upgrade to 1.18

 - Removed `perl-dev` from `makedepends` because this
   is a pure Perl module with no C code (it's `noarch`)
 - Moved `perl-test-mocktime-hires` from make to checkdepends
 - Moved `perl-module-util` to depends, as it is used in
   lib/DateTime/Format/Natural/Test.pm included in the .apk