Remove xournalpp dependency in flake

Readme.md

@@ -1,6 +1,9 @@
 # Sheet Organizer
 A simple tool for organizing and opening digital sheet music on a touch display as part of a digital music stand.
 
+## Dependencies
+This tool offers editing pdf using [Xournal++](https://github.com/xournalpp/xournalpp).
+
 ## Configuration
 You can configure sheet-organizer using an file `config.toml` inside one of your `$XDG_CONFIG_DIRECTORIES` (e.g. `~/.config/sheet-organizer/config.toml`).
 

flake.nix

@@ -52,7 +52,6 @@
               with pkgs;
               [
                 gtk4
-                xournalpp # not needed for building
               ]
               ++ pkgs.lib.optionals pkgs.stdenv.isDarwin [
                 # Additional darwin specific inputs can be set here