malcontent: Add malcontent-ui to passthru.tests

pkgs/development/libraries/malcontent/default.nix

···
 , glib-testing
 , python3
 , nixosTests
+, malcontent-ui
 }:
 
 stdenv.mkDerivation rec {
···
   passthru = {
     tests = {
       installedTests = nixosTests.installed-tests.malcontent;
+      inherit malcontent-ui;
     };
   };