[Dynamo] Fix function overrides (#120885)
To check existence of `__torch_function__`, the code intended to iterate each element but got `TupleVariable` when the ordinary `has_torch_function()` was being used. Needs further unpack in this case
Fixes #120653
Pull Request resolved: https://github.com/pytorch/pytorch/pull/120885
Approved by: https://github.com/yanboliang
