Update Task Paths for Mainnet Tasks

[ElliotFriedman]

Once we have our first mainnet task that will affect mainnet contracts, we should go through the repo and make sure that the monorepo integration tests point to the new mainnet directory. The justfiles single.just and nested.just may need to be updated too.

[blmalone]

For example, this file: https://github.com/ethereum-optimism/superchain-ops/blob/main/test/tasks/mock/example/fetch-tasks.sh#L27

[blmalone]

Completed.