[IntroRemoteDS-pre] L3_DataPreparation: Number of Cases reported for Country zero is wrong

## Where?
`L3_DataPreparation.ipynb` in `introduction-to-remote-data-science` branch.

## What?
The following sentence is not aligned with actual data: 
>So for instance, Country 0 had `1140` COVID cases at the start of when this data was collected (row 0), and only 451 when the data was last collected (row 53).

Initial COVID cases for `Country 0` is `2280` and not `1140` :)

HTH