Revert Merge #227168: opencl-headers: 2023.02.06 -> 2023.04.17

This reverts commit 7d61d759fdedee5757089c7ad9142c0e1832421c, reversing
changes made to 487f1a7723ed9728f76083a6de8dad7033f46dc1.

https://github.com/NixOS/nixpkgs/pull/227168#issuecomment-1539171566
It broke build of ocl-icd, and breaking changes are now not allowed.

pkgs/development/libraries/opencl-headers/default.nix

···
 
 stdenv.mkDerivation rec {
   pname = "opencl-headers";
-  version = "2023.04.17";
+  version = "2023.02.06";
 
   src = fetchFromGitHub {
     owner = "KhronosGroup";
     repo = "OpenCL-Headers";
     rev = "v${version}";
-    sha256 = "sha256-FK6pbIqNVVW9p6ozUVzuRxfxvibCA4cNFfhT22WjSzE=";
+    sha256 = "sha256-BJDaDokyHgmyl+bGqCwG1J7iOvu0E3P3iYZ1/krot8s=";
   };
 
   installPhase = ''