telegram-desktop: drop clang from nativeBuildInputs

There's no bundled libdispatch anymore, and older forks will gracefully fallback to QThreadPool impl

pkgs/applications/networking/instant-messengers/telegram/telegram-desktop/unwrapped.nix

@@ -6,7 +6,6 @@
   pkg-config,
   cmake,
   ninja,
-  clang,
   python3,
   qtshadertools,
   tdlib,
@@ -65,8 +64,6 @@ stdenv.mkDerivation (finalAttrs: {
     qtshadertools
   ]
   ++ lib.optionals stdenv.hostPlatform.isLinux [
-    # to build bundled libdispatch
-    clang
     gobject-introspection
   ]
   # Work around ld64's libc++ hardening issue causing Trace/BPT trap: 5