gui-e2e: xfail "test_add_top_list_widget"

Possible removal of web element selectable via get_attribute("placeholder")
causing 120s timeout in fixture setup results in a failing test case.

If not - a race condition needs to be handled, so that the
presence of expected web element is either validated
or something more meaningful is validated.

CMK-37975

Change-Id: I1feefad8586ca5b9bd17f4bbc7840f4f875c7dad

Author: dhsh-checkmk

tests/system/gui/test_dashboard.py

@@ -432,6 +432,7 @@ def test_widget_filters(
     ).to_have_count(hosts_count)
 
 
+@pytest.mark.xfail(reason="CMK-37975; skip failing test.")
 def test_add_top_list_widget(
     linux_hosts: list[str], cloned_linux_hosts_dashboard: CustomDashboard
 ) -> None: