python3Packages.jax: remove pytest-xdist

This dependency has caused nothing but trouble for us since its introduction. It offers moderate test suite speedups, but at the cost of frequent OOM failures in CI, including Hydra and nixpkgs-upkeep. Furthermore, the test suite takes only 1.5 CPU-hrs, limiting xdist's utility.

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

@@ -12,7 +12,6 @@
 , numpy
 , opt-einsum
 , pytestCheckHook
-, pytest-xdist
 , pythonOlder
 , scipy
 , stdenv
@@ -58,18 +57,13 @@ buildPythonPackage rec {
     jaxlib'
     matplotlib
     pytestCheckHook
-    pytest-xdist
   ];
 
-  # high parallelism will result in the tests getting stuck
-  dontUsePytestXdist = true;
-
   # NOTE: Don't run the tests in the expiremental directory as they require flax
   # which creates a circular dependency. See https://discourse.nixos.org/t/how-to-nix-ify-python-packages-with-circular-dependencies/14648/2.
   # Not a big deal, this is how the JAX docs suggest running the test suite
   # anyhow.
   pytestFlagsArray = [
-    "--numprocesses=4"
     "-W ignore::DeprecationWarning"
     "tests/"
   ];