Update to gotch 0.9.0

[jdrake]

Would be great to update transformer to work with https://github.com/sugarme/gotch/tree/v0.9.0

For example in /transformer/util/activation.go, the MustGelu method signature changed to accept a string and a bool:

func (g GeluActivation) Fwd(x *ts.Tensor) (retVal *ts.Tensor) {
	return x.MustGelu("???", false)
                           ^^^
}

[Chief-Alchemist]

Hitting the same issue, lets get this fixed

[aorticweb]

func (g GeluActivation) Fwd(x *ts.Tensor) (retVal *ts.Tensor) {
	return x.MustGelu("none", false)
}

you can replace with "none" or "tanh" according to libtorch docs