Skip the new IRB test on Windows for now

It's not passing from the beginning
https://github.com/ruby/ruby/runs/2550929220
https://ci.appveyor.com/project/ruby/ruby/builds/39100747

Author: k0kubun

test/irb/test_raise_no_backtrace_exception.rb

@@ -23,7 +23,7 @@ def test_raise_exception_with_invalid_byte_sequence
     end
 
     def test_raise_exception_with_different_encoding_containing_invalid_byte_sequence
-      skip if RUBY_ENGINE == 'truffleruby'
+      skip if RUBY_ENGINE == 'truffleruby' || /mswin|mingw/ =~ RUBY_PLATFORM
       backup_home = ENV["HOME"]
       Dir.mktmpdir("test_irb_raise_no_backtrace_exception_#{$$}") do |tmpdir|
         ENV["HOME"] = tmpdir