webkitgtk: don't use clang stdenv

Ughhhh this was terrible but it seems to now be fixed by [0].
Though it doesn't seem the issue is entirely resolved NixOS#36947.

[0]: NixOS#91293

pkgs/top-level/all-packages.nix

@@ -15677,7 +15677,6 @@ in
   webkitgtk = callPackage ../development/libraries/webkitgtk {
     harfbuzz = harfbuzzFull;
     inherit (gst_all_1) gst-plugins-base gst-plugins-bad;
-    stdenv = clangStdenv; # TODO: https://github.com/NixOS/nixpkgs/issues/36947
   };
 
   websocketpp = callPackage ../development/libraries/websocket++ { };