remove cmd.shared_params.dev special case

since --dev is a shortcut for --chain=dev and that case is managed in load_spec there is no need to manage it separately

(I had this branch for a while and I think it can be merged without problem)

requested review from @tuxmain

assigned to @HugoTrentesaux

changed the description

added RN-binary label

approved this merge request

mentioned in commit 9adbdf90

merged