countdown: disable as it stopped working

Signed-off-by: Rui Chen <rui@chenrui.dev>

Casks/c/countdown.rb

@@ -6,5 +6,11 @@ cask "countdown" do
   name "Countdown Screensaver"
   homepage "https://github.com/soffes/Countdown"
 
+  # no releases in the past 8 years, and no commits in the past 6 years
+  # users have reported that it stopped working
+  # https://github.com/soffes/Countdown/issues/8
+  # https://github.com/soffes/Countdown/issues/11
+  disable! date: "2024-01-01", because: :unmaintained
+
   screen_saver "Countdown.saver"
 end