bespokesynth: mark unfree

Binaries of VST2 cannot be distributed without upstream permission
which we don't have and cant get. Until VST2 support can be
teased out more carefully, let's mark the package us unfree.

pkgs/applications/audio/bespokesynth/default.nix

···
   meta = with lib; {
     description = "Software modular synth with controllers support, scripting and VST";
     homepage = "https://github.com/awwbees/BespokeSynth";
-    license = licenses.gpl3Plus;
+    license = with licenses; [
+      gpl3Plus
+      
+      # This package is unfree and not distributable due to the license of VST2.
+      # see #145607
+      unfree
+    ];
     maintainers = with maintainers; [ astro ];
     platforms = platforms.all;
   };