bpo-20175: Convert Modules/_multiprocessing to the Argument Clinic (GH-14245)

diff --git a/Modules/_multiprocessing/multiprocessing.h b/Modules/_multiprocessing/multiprocessing.h
index fe78135..277963b 100644
--- a/Modules/_multiprocessing/multiprocessing.h
+++ b/Modules/_multiprocessing/multiprocessing.h
@@ -88,6 +88,6 @@
  */
 
 extern PyTypeObject _PyMp_SemLockType;
-extern PyObject *_PyMp_sem_unlink(PyObject *ignore, PyObject *args);
+extern PyObject *_PyMp_sem_unlink(const char *name);
 
 #endif /* MULTIPROCESSING_H */