Remove poly variant from apply.ml for coq-of-ocaml
Reopening of !179 (merged)
The aim of this small MR is to name the type:
[`Success of context | `Failure]
with:
type success_or_failure = Success of context | Failure
in order to simplify the work of coq-of-ocaml to convert the protocol to Coq.
Part of a larger task "Lint the protocol for coq-of-ocaml" https://gitlab.com/nomadic-labs/tezos/-/issues/161