Add a comment about *not* caching the hash value. Issue #9685 suggested to…

Add a comment about *not* caching the hash value. Issue #9685 suggested to memorize the hash value, but the feature request was rejected because no speed ups were found.

Objects/tupleobject.c

@@ -322,6 +322,9 @@ error:
 
      1082527, 1165049, 1082531, 1165057, 1247581, 1330103, 1082533,
      1330111, 1412633, 1165069, 1247599, 1495177, 1577699
+
+   Tests have shown that it's not worth to cache the hash value, see
+   issue #9685.
 */
 
 static Py_hash_t