libretro-picodrive: remove patch that's no longer needed

emulators/libretro-picodrive/patches/patch-Makefile.libretro

@@ -1,28 +0,0 @@
-$NetBSD: patch-Makefile.libretro,v 1.2 2018/08/08 23:47:49 nia Exp $
-
-Don't redefine CC.
-
-Picodrive is written in C. Let's link with a C compiler instead of
-a C++ compiler.
-
---- Makefile.libretro.orig	2018-07-22 20:01:05.000000000 +0000
-+++ Makefile.libretro
-@@ -68,9 +68,6 @@ ifeq ($(platform), unix)
- 	DONT_COMPILE_IN_ZLIB = 1
- 	CFLAGS += -DFAMEC_NO_GOTOS
- 	use_sh2drc = 1
--ifneq ($(findstring SunOS,$(shell uname -a)),)
--	CC=gcc
--endif
- 
- # Portable Linux
- else ifeq ($(platform), linux-portable)
-@@ -656,7 +653,7 @@ else
- 	LD = link.exe
- endif
- else
--	LD = $(CXX)
-+	LD = $(CC)
- endif
- 
- include Makefile