pinentry-qt: fix caps lock warning

This fixes the following warning on plasma6:
> CapsLockWatcher was compiled without support for unix
> Checking for Caps Lock not possible on unsupported platform: "wayland"

pkgs/tools/security/pinentry/default.nix

···
   pkg-config,
   autoreconfHook,
   wrapGAppsHook3,
+  kdePackages,
   libgpg-error,
   libassuan,
   libsForQt5,
···
       buildInputs = [
         qt6.qtbase
         qt6.qtwayland
+        kdePackages.kguiaddons
       ];
       nativeBuildInputs = [ qt6.wrapQtAppsHook ];
     };