dev-perl/PerlIO-gzip: remove unused patch

Closes: https://github.com/gentoo/gentoo/pull/5337

dev-perl/PerlIO-gzip/files/perl-5.20-build.patch

@@ -1,12 +0,0 @@
---- a/Makefile.PL	2006-10-01 21:28:25.000000000 +0000
-+++ b/Makefile.PL	2014-01-23 15:40:56.784222851 +0000
-@@ -4,7 +4,8 @@
- use ExtUtils::MakeMaker;
- use Config;
- 
--unless ($Config{useperlio} eq 'define' and $Config{usesfio} eq 'false') {
-+unless ($Config{useperlio} eq 'define' and
-+	(defined($Config{usesfio}) ? $Config{usesfio} : 'false') eq 'false') {
-   die <<BARF;
- You need perl 5.8.0 or later, configured to use perlio (and not to use sfio)
- BARF