* Add gated-silu to t5 architecture to support UL2

* Fix error message

* formatting

* formatting again

* refactor

* fix classnames in _init_weights

* remove is_gated

* add test

* fix test

* Try without the test?

* Add back the test.

* Improve error message.

Co-authored-by: Daniel Hesslow <daniel@lighton.ai>