[Inductor] assert generator for random, dropout (#91833)

See comment https://github.com/pytorch/pytorch/pull/90869#discussion_r1063731541 , https://github.com/pytorch/pytorch/pull/91673#discussion_r1061099337.

Pull Request resolved: https://github.com/pytorch/pytorch/pull/91833
Approved by: https://github.com/jansel
diff --git a/torch/_decomp/decompositions.py b/torch/_decomp/decompositions.py
index 631d34e..607b7ac 100644
--- a/torch/_decomp/decompositions.py
+++ b/torch/_decomp/decompositions.py
@@ -1516,6 +1516,7 @@
 @register_decomposition(aten._fused_dropout)
 @pw_cast_for_opmath
 def _fused_dropout_decomposition(input, p, generator=None):
+    assert generator is None
     mask = (torch.rand_like(input) < p).to(dtype=torch.uint8)
     res = mask.type_as(input) * input * (1.0 / p)
     return (res, mask)