Unused `wasm_code_name`

[grarco]

This function is unused. https://github.com/anoma/namada/blob/427a57cab8c93a18f293b00e9f54e6e9da5ac147/crates/core/src/storage.rs#L554

It only appears in init_chain where we write the value to storage but we never read it. It was used in v1 of masp fee payment to retrieve the hash of the transfer tx from storage. Since the logic has changed this is now useless. We could consider removing it together with the actual keys in storage even though this is a state-breaking change.