xdg-desktop-portal: Disable test failing with libportal 0.9.0

libportal before version 0.9.0 used to pass the notification GVariant
directly to the x-d-p D-Bus API. When the test tried to add a notification
with an unsupported property, the x-d-p D-Bus API would return an error
and libportal would report it.

libportal 0.9.0 started to filter out unsupported properties so the test is now pointless:
https://github.com/flatpak/libportal/commit/ca6f8e3593bd1f1f25983ac6f63d1e0f6e48a47e

Though the next x-d-p version will actually start to filter the unsupported properties as well.
The test will then be modified to check the filtering happens:
https://github.com/flatpak/xdg-desktop-portal/commit/bf29961854a2b8a6dee3f054aa0fd16a6a66486c

pkgs/development/libraries/xdg-desktop-portal/default.nix

@@ -147,6 +147,14 @@ stdenv.mkDerivation (finalAttrs: {
     # until/unless bubblewrap ships a pkg-config file, meson has no way to find it when cross-compiling.
     substituteInPlace meson.build \
       --replace-fail "find_program('bwrap'"  "find_program('${lib.getExe bubblewrap}'"
+
+    # Disable test failing with libportal 0.9.0
+    ${
+      assert (lib.versionOlder finalAttrs.version "1.20.0");
+      "# TODO: Remove when updating to x-d-p 1.20.0"
+    }
+    substituteInPlace tests/test-portals.c \
+      --replace-fail 'g_test_add_func ("/portal/notification/bad-arg", test_notification_bad_arg);' ""
   '';
 
   preCheck = ''