Remove obsolete bin/update script

This script was removed from Rails in Rails 6.0 [1] because the
`bin/setup` script is now idempotent and can be used to update the
application as well.

[1] See https://github.com/rails/rails/commit/8927eba83c

bin/update

@@ -1,28 +0,0 @@
-#!/usr/bin/env ruby
-require "fileutils"
-include FileUtils
-
-# path to your application root.
-APP_ROOT = File.expand_path("..", __dir__)
-
-def system!(*args)
-  system(*args) || abort("\n== Command #{args} failed ==")
-end
-
-chdir APP_ROOT do
-  # This script is a way to update your development environment automatically.
-  # Add necessary update steps to this file.
-
-  puts "== Installing dependencies =="
-  system! "gem install bundler --conservative"
-  system("bundle check") || system!("bundle install")
-
-  puts "\n== Updating database =="
-  system! "bin/rails db:migrate"
-
-  puts "\n== Removing old logs and tempfiles =="
-  system! "bin/rails log:clear tmp:clear"
-
-  puts "\n== Restarting application server =="
-  system! "bin/rails restart"
-end