Use exit! instead of exit (#602)

We found that using `exit` here would conflict with the `debug` gem on Ruby 3.2. It would hang and never exit when tests completed, similar to this issue: ruby/debug#336 (comment)

lib/teaspoon/utility.rb

@@ -7,7 +7,7 @@ def self.root
 
   def self.abort(message = nil, code = 1)
     STDOUT.print("#{message}\n") if message
-    exit(code)
+    exit!(code)
   end
 
   module Utility