EVM/Node: remove validation's encoding

Follow up of !15958 (merged).

I did this in a different merge request because I thought it was going to be tricky to remove this part of the code. The node uses a retro compatible way to call the simulation, because we can do imulation on old kernels, so I wanted to isolate this change to make sure I don't break anything.

The node was supposed to handle both (transaction_object, address) either because first iteration of kernel validation was returning only the address, but it has been a while since we return only transaction object (way older than Bifrost). But anyway, we don't care, the node simulation always return transaction_object