Remove the unused USDC IBC asset from upgrade-test state

[linear]

Why

The simulated network used by the chain upgrade test carries a bridged USDC asset that deployments don't use. It adds irrelevant state to the test and noise to the deployment and balance checks, making the test harder to reason about.

What

Remove the unused bridged USDC asset and any handling tied to it from the upgrade test's simulated state, since it isn't relevant to deployments or their balances.

Acceptance Criteria

• The upgrade test no longer sets up or migrates the unused USDC asset
• The upgrade test passes without it