fix: CodeCID should be at end of model

[kasteph]

CSVs produced follow the order of the definition in the model. So CSVs of actors produced with this model definition are ordered like so:

height,id,state_root,code,code_cid,head,balance,nonce,state

This is problematic when inserting CSVs to other data sources as one then has to create these two columns before the change is introduced and fill these null values manually (really only a problem for code_cid which is in the middle of the table).

Note that Postgres doesn't have this issue (new columns are appended at the end).

[birdychang]

Thanks!