Why this change?
The test became flaky due to d208396c5c495301cf301426a4166006ffb1d285.
In that commit, we introduced `page.has_no_css?("div.menu-panel.animating")` to `PageObjects::Components::NavigationMenu::Sidebar#open_on_mobile` but
it did not work as intended because `page.has_no_css?("div.menu-panel.animating")` can return `true` immediately as the `animating` class has not been added
to the element.
What does this change do?
Switch to the `wait_for_animation` system helper to ensure that all
animations have ended on the element.