python3Packages.flet: mark broken

It fails to build with

    pyproject_hooks._impl.BackendUnavailable: Cannot import 'setuptools.build_meta'

but adding setuptools to the build-system and updating the dependencies
is not sufficient to make it build.

pkgs/development/python-modules/flet/default.nix

@@ -74,6 +74,7 @@ buildPythonPackage rec {
   pythonImportsCheck = [ "flet" ];
 
   meta = {
+    broken = true;
     description = "Framework that enables you to easily build realtime web, mobile, and desktop apps in Python";
     homepage = "https://flet.dev/";
     changelog = "https://github.com/flet-dev/flet/releases/tag/v${version}";