fix: move importedModels key up to defineData

[dpilch]

Description of changes

fix: move importedModels key up to defineData. It should be like the following (not nested under importedAmplifyDynamoDBTableMap).

export const data = defineData({
  importedAmplifyDynamoDBTableMap: { Todo: "my-todo-mapping" },
  importedModels: ["Todo"],
  schema: "TODO: Add your existing graphql schema here"
});

Issue #, if available

N/A

Description of how you validated changes

Add new unit test.

Checklist

• PR description included
• yarn test passes
• Tests are changed or added

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