upgrade --all: use odeprecated.

Library/Homebrew/cmd/upgrade.rb

@@ -25,13 +25,7 @@ module Homebrew
 
     Homebrew.perform_preinstall_checks
 
-    if ARGV.include?("--all")
-      opoo <<~EOS
-        We decided to not change the behaviour of `brew upgrade` so
-        `brew upgrade --all` is equivalent to `brew upgrade` without any other
-        arguments (so the `--all` is a no-op and can be removed).
-      EOS
-    end
+    odeprecated "'brew upgrade --all'", "'brew upgrade'" if ARGV.include?("--all")
 
     if ARGV.named.empty?
       outdated = Formula.installed.select do |f|