remove require of files under support that do not use

I do not know why files under the support has been require.
However, under the support even rails application does not use.
In addition, since the default under the support file nor is generated, it requires I think not necessary

railties/lib/rails/generators/rails/plugin/templates/test/test_helper.rb

@@ -14,9 +14,6 @@
 # to be shown.
 Minitest.backtrace_filter = Minitest::BacktraceFilter.new
 
-# Load support files
-Dir["#{File.dirname(__FILE__)}/support/**/*.rb"].each { |f| require f }
-
 # Load fixtures from the engine
 if ActiveSupport::TestCase.respond_to?(:fixture_path=)
   ActiveSupport::TestCase.fixture_path = File.expand_path("../fixtures", __FILE__)