[ruby/logger] Ignored loading CoreAssertions in test runner

https://github.com/ruby/logger/commit/2fd5401ad6

test/logger/helper.rb

@@ -1,13 +0,0 @@
-ROOT_DIR = File.dirname(__dir__)
-$LOAD_PATH.unshift File.join(ROOT_DIR, 'lib') # to use logger in this repo instead of ruby built-in logger
-$LOAD_PATH.unshift File.join(ROOT_DIR, 'test', 'lib') # to use custom test-unit in this repo
-require 'logger'
-require 'test/unit'
-
-begin
-  # for standalone test suite on ruby/logger
-  require 'core_assertions'
-
-  Test::Unit::TestCase.include Test::Unit::CoreAssertions
-rescue LoadError
-end

test/logger/test_logdevice.rb

@@ -1,6 +1,6 @@
 # coding: US-ASCII
 # frozen_string_literal: false
-require_relative 'helper'
+require 'logger'
 require 'tempfile'
 require 'tmpdir'
 

test/logger/test_logger.rb

@@ -1,6 +1,6 @@
 # coding: US-ASCII
 # frozen_string_literal: false
-require_relative 'helper'
+require 'logger'
 require 'tempfile'
 
 class TestLogger < Test::Unit::TestCase

test/logger/test_logperiod.rb

@@ -1,6 +1,6 @@
 # coding: US-ASCII
 # frozen_string_literal: false
-require_relative 'helper'
+require 'logger'
 require 'time'
 
 class TestLogPeriod < Test::Unit::TestCase

test/logger/test_severity.rb

@@ -1,6 +1,6 @@
 # coding: US-ASCII
 # frozen_string_literal: false
-require_relative 'helper'
+require 'logger'
 
 class TestLoggerSeverity < Test::Unit::TestCase
   def test_enum