Remove useless code in test/test_helper.rb

This PR removes useless code in test/test_helper.rb.

Author: koic

test/test_helper.rb

@@ -1,8 +1,5 @@
 # frozen_string_literal: true
 
-ENV["RAILS_ENV"] ||= "test"
-
-require "bundler/setup"
 require "mcp"
 
 require "minitest/autorun"
@@ -18,8 +15,3 @@
 require_relative "instrumentation_test_helper"
 
 Minitest::Reporters.use!(Minitest::Reporters::ProgressReporter.new)
-
-module ActiveSupport
-  class TestCase
-  end
-end