chore: upgrade rails to 7.0 and other dependencies

config/boot.rb

@@ -2,9 +2,6 @@
 
 ENV["BUNDLE_GEMFILE"] ||= File.expand_path("../Gemfile", __dir__)
 
-$stdout.sync = true
-$stderr.sync = true
-
 require "bundler/setup" # Set up gems listed in the Gemfile.
 
 require_relative "../lib/postal/config"