perl: Do not insist on Perl 5.28 or higher

We have no special requirements here.
Signed-off-by: Michael Tremer <michael.tremer@ipfire.org>

src/perl/Makefile.PL

-use 5.028001;
 use ExtUtils::MakeMaker;
 # See lib/ExtUtils/MakeMaker.pm for details of how to influence
 # the contents of the Makefile that is written.