Michelson: remove the infinite cases in dep_step_eq
Some cases in the proof of https://nomadic-labs.gitlab.io/coq-tezos-of-ocaml/docs/proofs/script_interpreter#dep_step_eq were too slow (probably infinite). This MR fixes that and verifies a few more cases.
Fix https://gitlab.com/nomadic-labs/coq-tezos-of-ocaml/-/issues/116
Edited by Guillaume Claret