Ban passing in free function into capture_pre_autograd_graph (#120817)
Summary: Today we don't allow free functions to be tracing callable in torch.export. As a part of migrating capture_preautograd_graph usages to torch.export, we need to ban free functions to capture_preautograd_graph as well
Test Plan: CI
Differential Revision: D54319597
Pull Request resolved: https://github.com/pytorch/pytorch/pull/120817
Approved by: https://github.com/zhxchen17, https://github.com/andrewor14
