Remove rails/test_helper require from legacy specs

This causes the minitest test runner to be loaded: this test runner
does not recognise the `--pattern` option and returns a non-zero exit
code.

Signed-off-by: Alex Coles <alex@alexbcoles.com>

test/test_helper.rb

@@ -36,7 +36,7 @@ if ENV['CI'] == 'true'
 end
 
 require File.expand_path('../../config/environment', __FILE__)
-require 'rails/test_help'
+
 require 'fileutils'
 require 'rspec/mocks'