Skip testing oom killer on Python 3.12

Need to investigate further if there's a safe way to do this test.

tests/test_concurrency.py

@@ -4,6 +4,7 @@
 from __future__ import annotations
 
 import os
+import platform
 
 import pytest
 
@@ -13,6 +14,9 @@ from .conftest import run_ocrmypdf_api
 
 
 @pytest.mark.skipif(os.name == 'nt', reason="Windows doesn't have SIGKILL")
+@pytest.mark.skipif(
+    platform.python_version_tuple() >= ('3', '12'), reason="can deadlock due to fork"
+)
 def test_simulate_oom_killer(multipage, no_outpdf):
     exitcode = run_ocrmypdf_api(
         multipage,