Drop redundant assert.

Author: Yhg1s

Python/bytecodes.c

@@ -3154,7 +3154,6 @@ dummy_func(
             assert(_PyObject_IsUniquelyReferenced(iter_o));
 #endif
             assert(seq);
-            assert(it->it_index >= 0);
             assert(it->it_index < PyTuple_GET_SIZE(seq));
             next = PyStackRef_FromPyObjectNew(PyTuple_GET_ITEM(seq, it->it_index++));
         }