meta: Drop docker (again)

Docker feels a bit too old school after being spoiled by the Nix
language and all the features that NixOS provides. Dockerfiles are not
as cool to write as Nix files and docker-compose.yml lacks many of the
reproducible benefits one gets from sticking with Nix.

Now that I have more experience with Nix, it should be possible for me
to build and run the services I want to run with Nix instead of Docker.
This should additionally reduce my personal machine's startup time,
which was already quite low with Hyprland.

As a final closing, expertise in Nix seems more useful than Docker for
my personal goals. I'd rather be able to control entire Linux systems
and their full environments with containers, virtual machines, and other
goodies than be restricted to the simplistic model that is Docker.

modules/docker.nix

@@ -1,10 +0,0 @@
-{ pkgs, ... }:
-
-{
-  virtualisation.docker.enable = true;
-  virtualisation.docker.enableOnBoot = false;
-
-  environment.systemPackages = with pkgs; [
-    docker-compose
-  ];
-}