glimmerblocker: use deprecate! instead of discontinued

Casks/g/glimmerblocker.rb

@@ -7,6 +7,8 @@ cask "glimmerblocker" do
   desc "HTTP based ad blocker"
   homepage "https://glimmerblocker.org/"
 
+  deprecate! date: "2023-12-17", because: :discontinued
+
   pkg "GlimmerBlocker.pkg"
 
   uninstall pkgutil:   "org.glimmerblocker.pkg",
@@ -23,8 +25,6 @@ cask "glimmerblocker" do
   ]
 
   caveats do
-    discontinued
-
     <<~EOS
       You must deactivate GlimmerBlocker from the installed preference
       pane before uninstalling. See https://glimmerblocker.org/wiki/Uninstall.