docker: move default from 20.10 to 24

Docker CE 20.10 seems to stop receiving security updates and bug fixes
after December 10, 2023[1].

1. https://github.com/moby/moby/discussions/45104

There is public commitment for longer maintenance and then it seems
risky to default to it during 23.11 life-cycle.

Signed-off-by: Otavio Salvador <[e-mail]>

nixos/doc/manual/release-notes/rl-2311.section.md

···
 
 - The Linux kernel module `msr` (see [`msr(4)`](https://man7.org/linux/man-pages/man4/msr.4.html)), which provides an interface to read and write the model-specific registers (MSRs) of an x86 CPU, can now be configured via `hardware.cpu.x86.msr`.
 
+- Docker now defaults to 24, as 20.10 is stopping to receive security updates and bug fixes after [December 10, 2023](https://github.com/moby/moby/discussions/45104).
+
 - There is a new NixOS option when writing NixOS tests `testing.initrdBackdoor`, that enables `backdoor.service` in initrd. Requires `boot.initrd.systemd.enable` to be enabled. Boot will pause in stage 1 at `initrd.target`, and will listen for commands from the `Machine` python interface, just like stage 2 normally does. This enables commands to be sent to test and debug stage 1. Use `machine.switch_root()` to leave stage 1 and proceed to stage 2.

pkgs/top-level/all-packages.nix

···
   inherit (callPackage ../applications/virtualization/docker {})
     docker_20_10 docker_24;
 
-  docker = docker_20_10;
+  docker = docker_24;
   docker-client = docker.override { clientOnly = true; };
 
   docker-proxy = callPackage ../applications/virtualization/docker/proxy.nix { };