batches: fix missing mocks for batch change not found story

Created by: courier-new

At some point (probably in the week before beta launch when EVERYTHING was happening 🙂) the mock data requirements for the EditBatchSpecPage storybook stories changed, and the story for when the batch change is not found broke. This just supplies mock data for the missing request.

Test plan

Verified storybook story no longer throws error.

App preview:

• Web
• Storybook

Check out the client app preview documentation to learn more.