Update episode 9 to refer to the new cmorizer interface

[remi-kazeroni]

Describe the bug
A new set of commands is available to handle observational datasets. This was introduced in ESMValGroup/ESMValTool#1657 As a consequence, the cmorizer command was changed from cmorizer_obs -o DATASET to esmvaltool data format DATASET. Additionally, we have a few new commands to download data from source, display information on a given dataset, show the list of supported datasets (see ESMValGroup/ESMValTool#2560). It could be useful to mention some of these in the episode 9 of the Tutorial.

I will work on that after ESMValTool v2.5 is released. At the moment, the new cmorizer interface is only available in the development installation.