relax assertion on fake shape (#121599)
Summary: Seems like if you use `capture_pre_autograd_graph` fake tensor shapes can be ints instead of symints.
Test Plan: fixes the AssertionError in N5057219
Differential Revision: D54729142
Pull Request resolved: https://github.com/pytorch/pytorch/pull/121599
Approved by: https://github.com/angelayi, https://github.com/BoyuanFeng
