cleanup Ellipsis and NotImplemented strings after we're done

Modules/_pickle.c

@@ -2815,18 +2815,24 @@ static int
 save_ellipsis(PicklerObject *self, PyObject *obj)
 {
     PyObject *str = PyUnicode_FromString("Ellipsis");
+    int res;
     if (str == NULL)
         return -1;
-    return save_global(self, Py_Ellipsis, str);
+    res = save_global(self, Py_Ellipsis, str);
+    Py_DECREF(str);
+    return res;
 }
 
 static int
 save_notimplemented(PicklerObject *self, PyObject *obj)
 {
     PyObject *str = PyUnicode_FromString("NotImplemented");
+    int res;
     if (str == NULL)
         return -1;
-    return save_global(self, Py_NotImplemented, str);
+    res = save_global(self, Py_NotImplemented, str);
+    Py_DECREF(str);
+    return res;
 }
 
 static int