Remove work-around for gh-135335 now it has been fixed.

Remove unnecessary rc check.

Author: duaneg

Lib/test/_test_multiprocessing.py

@@ -6901,9 +6901,8 @@ def test_preload_main(self):
             self.skipTest("forkserver specific test")
 
         name = os.path.join(os.path.dirname(__file__), 'mp_preload_main.py')
-        rc, out, err = test.support.script_helper.assert_python_ok(name)
+        _, out, err = test.support.script_helper.assert_python_ok(name)
         self.assertFalse(err, msg=err.decode())
-        self.assertEqual(rc, 0)
 
         # TODO: Where is the extra empty line coming from?
         out = out.decode().split("\n")

Lib/test/mp_preload_main.py

@@ -1,13 +1,7 @@
 import multiprocessing
-import sys
 
 print(f"{__name__}")
 
-# TODO: This is necessary as the fork server doesn't flush output after
-#       preloading modules, and hence buffered output is inherited by child
-#       processes. See gh-135335 (this should be removed once that is fixed).
-sys.stdout.flush()
-
 def f():
     print("f")