fix test for subprocess (#16644)

Lib/test/test_subprocess.py

@@ -2154,15 +2154,12 @@ class ContextManagerTests(BaseTestCase):
             self.assertEqual(proc.returncode, 1)
 
     def test_invalid_args(self):
-        with self.assertRaises(OSError) as c:
+        with self.assertRaises(FileNotFoundError) as c:
             with subprocess.Popen(['nonexisting_i_hope'],
                                   stdout=subprocess.PIPE,
                                   stderr=subprocess.PIPE) as proc:
                 pass
 
-            if c.exception.errno != errno.ENOENT:  # ignore "no such file"
-                raise c.exception
-
 
 def test_main():
     unit_tests = (ProcessTestCase,