Make the docs ready for 2.4

| Q             | A
| ------------- | ---
| Doc fix?      | yes
| New docs?     | no
| Applies to    | 2.4+
| Fixed tickets | -

Things to do when 2.4 is released:

 * update the installation instructions to use 2.4 instead of 2.3 (`book/installation`, `components/using_components` and `quick_tour/the_big_picture`)