Prefer to use File.readlines instead of IO.readlines

lib/rdoc/rd/block_parser.rb

@@ -360,7 +360,7 @@ def get_included(file)
     file_name = File.join dir, file
 
     if File.exist? file_name then
-      included = IO.readlines file_name
+      included = File.readlines file_name
       break
     end
   end

test/ruby/enc/test_regex_casefold.rb

@@ -19,7 +19,7 @@ class TestCaseFold < Test::Unit::TestCase
   end
 
   def read_tests
-    IO.readlines("#{UNICODE_DATA_PATH}/CaseFolding.txt", encoding: Encoding::ASCII_8BIT)
+    File.readlines("#{UNICODE_DATA_PATH}/CaseFolding.txt", encoding: Encoding::ASCII_8BIT)
     .collect.with_index { |linedata, linenumber| [linenumber.to_i+1, linedata.chomp] }
     .reject { |number, data| data =~ /^(#|$)/ }
     .collect do |linenumber, linedata|

test/ruby/test_exception.rb

@@ -1266,7 +1266,7 @@ $stderr = $stdout; raise "\x82\xa0"') do |outs, errs, status|
     begin;
       class Bug < RuntimeError
         def backtrace
-          IO.readlines(IO::NULL)
+          File.readlines(IO::NULL)
         end
       end
       bug = Bug.new '[ruby-core:85939] [Bug #14577]'

test/test_unicode_normalize.rb

@@ -24,7 +24,7 @@ class TestUnicodeNormalize
   NormTest = Struct.new :source, :NFC, :NFD, :NFKC, :NFKD, :line
 
   def self.read_tests
-    lines = IO.readlines(expand_filename('NormalizationTest'), encoding: 'utf-8')
+    lines = File.readlines(expand_filename('NormalizationTest'), encoding: 'utf-8')
     firstline = lines.shift
     define_method "test_0_normalizationtest_firstline" do
       assert_include(firstline, "NormalizationTest-#{UNICODE_VERSION}.txt")