bpo-33608: Fix PyEval_InitThreads() warning (GH-12346)

The function has no return value.

Fix the following warning on Windows:

    python\ceval.c(180): warning C4098: 'PyEval_InitThreads':
    'void' function returning a value

Python/ceval.c

@@ -177,7 +177,7 @@ PyEval_InitThreads(void)
 
     _PyRuntime.ceval.pending.lock = PyThread_allocate_lock();
     if (_PyRuntime.ceval.pending.lock == NULL) {
-        return Py_FatalError("Can't initialize threads for pending calls");
+        Py_FatalError("Can't initialize threads for pending calls");
     }
 }