[Data layer codelab] Section 7 (Create the task repository) should reuse mapped data

Here:
`suspend fun refresh() {
val networkTasks = networkDataSource.loadTasks()
localDataSource.deleteAll()
val localTasks = withContext(dispatcher) {
networkTasks.toLocal()
}
localDataSource.upsertAll(networkTasks.toLocal())
}`

The last line should probably read:
`localDataSource.upsertAll(networkTasks.toLocal())`

Start in the Section 7 data layer codelab at the suspend refresh() function and compare the mapped localTasks value with the argument passed to localDataSource.upsertAll(). Done means the already-mapped local data is reused consistently in the repository example.

Written by the indexing model from the issue text.