Delete some unused system packages

system/nyxt.nix

@@ -1,10 +0,0 @@
-{ pkgs, ... }: {
-  environment.systemPackages = with pkgs; [
-    nyxt
-    gst_all_1.gst-libav
-    gst_all_1.gst-plugins-base
-    gst_all_1.gst-plugins-good
-    gst_all_1.gst-plugins-bad
-    gst_all_1.gst-plugins-ugly
-  ];
-}

system/plasma.nix

@@ -1,20 +0,0 @@
-{ pkgs, ... }: {
-  imports = [ ./desktop.nix ];
-  environment.systemPackages = with pkgs;
-    with libsForQt5; [
-      plasma-wayland-protocols
-      plasma-integration
-      plasma-browser-integration
-      plasma-thunderbolt
-      kwin-tiling
-      krdc
-    ];
-  services.xserver = {
-    enable = true;
-    desktopManager.plasma5.enable = true;
-    displayManager.sddm = {
-      enable = true;
-      settings = { General = { InputMethod = ""; }; };
-    };
-  };
-}