Update Drupal example in Chapter 4 to latest version (9.x)

[geerlingguy]

See title; I want to get it to latest stable version prior to the next book release.

[geerlingguy]

This update will also likely require some updates to other parts of the example, like the underlying OS (for newer DB version), PHP version to 7.4, Composer to maybe Composer 2(?), Drush to 10.x.

[geerlingguy]

Opened an issue with the composer module here: ansible-collections/community.general#725

(Since I'm going to switch to using Composer to set up the Drupal project and install Drush now—it's just too hard/annoying to try to do it all via Git checkouts anymore).

[geerlingguy]

Fixed in the manuscript. Will be in the next version of the book.