actual: use deprecate! instead of discontinued

Casks/a/actual.rb

@@ -11,6 +11,8 @@ cask "actual" do
   desc "Privacy-focused app for managing your finances"
   homepage "https://actualbudget.com/"
 
+  deprecate! date: "2023-12-17", because: :discontinued
+
   app "Actual.app"
 
   zap trash: [
@@ -20,8 +22,4 @@ cask "actual" do
     "~/Library/Preferences/com.shiftreset.actual.plist",
     "~/Library/Saved Application State/com.shiftreset.actual.savedState",
   ]
-
-  caveats do
-    discontinued
-  end
 end