Filter-Simple: Correct ambiguous assignment to INSTALLDIRS

[jkeenan]

Consider this excerpt from dist/Filter-Simple/Makefile.PL:

  1 require 5.006; # uses 'our'
  2 use strict;
  3 use ExtUtils::MakeMaker;
  4 WriteMakefile(
  5     'NAME'          => 'Filter::Simple',
  6     'VERSION_FROM'  => 'lib/Filter/Simple.pm',
  7     'INSTALLDIRS'   => 'perl',
  8     'LICENSE'       => 'perl_5',
  9     'INSTALLDIRS'   => ( $] < 5.011 ? 'perl' : 'site' ),
...

Note that INSTALLDIRS gets assigned to twice, once at line 7 and once at line 9. This is potentially confusing to any future maintainer of this library or anyone who does a CPAN release.

Please review this pull request.

And speaking of CPAN releases ...

In blead, Filter-Simple is at version 0.96. Up on CPAN, it's still at version 0.94 and hasn't had a CPAN release since August 2017.