ModuleError out of sync, fails to deserialize --dry-run error

[ascjones]

Since paritytech/substrate#10242, the error field on ModuleError is now a [u8; 4], and in the released version of sp_runtime we depend upon it is still a u8.

So when we call instantiate/call with --dry-run and it triggers a ContractTrapped or any other internal pallet_contracts error, the returned error fails to deserialize because of the incompatible ModuleError types: it expects a u8 but receives a [u8; 4].

One solution would be to do a new sp_runtime release in substrate with the new struct, though that has the downside of not being backwards compatible. But we may not even want to be backwards compatible until contracts are actually on a production chain somewhere.