remove default lower bound in dynamic_dim suggestions (#101636)
So instead of `2 <= dynamic_dim(x, 0)` simply suggest `dynamic_dim(x, 0)`. This has exactly the same effect.
Differential Revision: [D45933273](https://our.internmc.facebook.com/intern/diff/D45933273/)
Pull Request resolved: https://github.com/pytorch/pytorch/pull/101636
Approved by: https://github.com/tugsbayasgalan, https://github.com/ydwu4
