Update references from statemint-local to asset-hub-rococo-local on zombinet configuration files

[weezy20]

For local trappist playground example here and among other configs under trappist/zombienet the local asset-hub parachain uses statemint-local as the chainspec which now would just point to asset-hub-polkadot invalidating the assumption for a user playing with a fresh local asset-hub parachain.

chain would need to be updated to use asset-hub-rococo-local instead

[[parachains]]
id = 1000
add_to_genesis = true
cumulus_based = true
chain = "statemine-local"

[stiiifff]

Fixed by #325