Revert "python3Packages.materialx: 1.38.10 -> 1.39.1"

This reverts commit 993ec32.
MaterialX has some upstream issues which haven't been quite
worked out, yet[1]. It is therefore reasonable to wait
with an update in nixpkgs. It also breaks downstream packages
like python312Packages.openusd as well as blender[2]

[1]: PixarAnimationStudios/OpenUSD#3159
[2]: NixOS#326466 (comment)

Signed-off-by: Florian Brandes <[email protected]>

Author: gador

pkgs/development/python-modules/materialx/default.nix

@@ -17,13 +17,13 @@
 
 buildPythonPackage rec {
   pname = "materialx";
-  version = "1.39.1";
+  version = "1.38.10";
 
   src = fetchFromGitHub {
     owner = "AcademySoftwareFoundation";
     repo = "MaterialX";
-    rev = "refs/tags/v${version}";
-    hash = "sha256-WzzsY1hOWwJEqT/ZRLIoZDfKNvx1Yf6aFhA3ZcSPx+s=";
+    rev = "v${version}";
+    hash = "sha256-/kMHmW2dptZNtjuhE5s+jvPRIdtY+FRiVtMU+tiBgQo=";
   };
 
   format = "other";