libidn2: drop Darwin error patch

This patch is no longer needed to build libidn2 on Darwin, which can use
the implementation of `error` from gnulib. This fixes compliation with
clang 16, which fails due to other uses of implicity-declared `error`
that it rejects (due to the removal of `#include "error.h"` in the patch).

pkgs/development/libraries/libidn2/default.nix

@@ -18,8 +18,6 @@ stdenv.mkDerivation rec {
   # Beware: non-bootstrap libidn2 is overridden by ./hack.nix
   outputs = [ "bin" "dev" "out" "info" "devdoc" ];
 
-  patches = lib.optional stdenv.isDarwin ./fix-error-darwin.patch;
-
   enableParallelBuilding = true;
 
   # The above patch causes the documentation to be regenerated, so the

pkgs/development/libraries/libidn2/fix-error-darwin.patch

@@ -1,20 +0,0 @@
-diff --git a/src/idn2.c b/src/idn2.c
-index 6abbc72..804f0f2 100644
---- a/src/idn2.c
-+++ b/src/idn2.c
-@@ -31,7 +31,6 @@
- #include <unistr.h>
- 
- /* Gnulib headers. */
--#include "error.h"
- #include "gettext.h"
- #define _(String) dgettext (PACKAGE, String)
- #include "progname.h"
-@@ -222,7 +219,7 @@ main (int argc, char *argv[])
-     }
- 
-   if (ferror (stdin))
--    error (EXIT_FAILURE, errno, "%s", _("input error"));
-+    perror (_("input error"));
- 
-   cmdline_parser_free (&args_info);