orc: fix build on 32-bit ARM

In 0.4.36, the sed expression that tries to disable the exec_opcodes_sys
test also deletes other lines that break the file syntax. The build
fails with:

testsuite/meson.build:23:25: ERROR: Expecting endif got colon.
                  install: false,
                         ^
For a block that started at 22,2
  if enabled_backends.contains('sse') and enabled_backends.contains('avx')
  ^

The test has apparently been fixed since 0.4.33 anyway (see [1]), so
just get rid of this sed patch.

[1] 5d5515ea5b

pkgs/development/compilers/orc/default.nix

@@ -25,10 +25,7 @@ in stdenv.mkDerivation rec {
     sha256 = "sha256-g7B0y2cxfVi+8ejQzIYveuinekW7/wVqH5h8ZIiy9f0=";
   };
 
-  postPatch = lib.optionalString stdenv.isAarch32 ''
-    # https://gitlab.freedesktop.org/gstreamer/orc/-/issues/20
-    sed -i '/exec_opcodes_sys/d' testsuite/meson.build
-  '' + lib.optionalString (stdenv.isDarwin && stdenv.isx86_64) ''
+  postPatch = lib.optionalString (stdenv.isDarwin && stdenv.isx86_64) ''
     # This benchmark times out on Hydra.nixos.org
     sed -i '/memcpy_speed/d' testsuite/meson.build
   '';