dustbowl: update linux kernel version + rm unneeded packages

nixos/dustbowl.nix

@@ -42,7 +42,7 @@
   ];
 
   # Kernel version
-  boot.kernelPackages = pkgs.linuxPackages_5_15;
+  boot.kernelPackages = pkgs.linuxKernel.packages.linux_6_18;
 
   # Use the systemd-boot EFI boot loader.
   # boot.loader.systemd-boot.enable = true;
@@ -165,6 +165,7 @@
 
   environment.systemPackages = with pkgs; [
     ntfs3g
+    man-pages
 
     # CLI utilities
     file
@@ -206,7 +207,6 @@
 
     # Services
     syncthing
-    nextcloud-client
     mpd
 
     # GTK theme
@@ -247,7 +247,6 @@
     signal-desktop
     element-desktop
     wasistlos
-    # fluffychat # FIXME insecure, see https://github.com/NixOS/nixpkgs/pull/334638#issuecomment-2289025802
 
     (callPackage ./posy-cursor-black.nix { })
   ];