Document changing menus of raspi-config

[aallan]

The options on raspi-config will now change depending on which Raspberry Pi hardware it's running on post-Bookworm. This needs documenting. The decision I've made for #2955 is to document the Pi 4 case only right now with a NOTE to say that there will be changes depending on what hardware you're on.

We probably need to document this properly at some point, but I don't see it as urgent.

[aallan]

Low priority one @nathan-contino