Re-skip an unstable Ractor test

https://github.com/ruby/ruby/actions/runs/4316423442/jobs/7532190115
http://ci.rvm.jp/results/trunk-yjit@ruby-sp2-docker/4466770

bootstraptest/test_ractor.rb

@@ -1673,6 +1673,7 @@ assert_equal '30', %q{
 }
 
 # Selector#wait can support dynamic addition
+yjit_enabled = ENV.key?('RUBY_YJIT_ENABLE') || ENV.fetch('RUN_OPTS', '').include?('yjit')
 assert_equal '600', %q{
   RN = 100
   s = Ractor::Selector.new
@@ -1699,7 +1700,7 @@ assert_equal '600', %q{
   end
 
   h.sum{|k, v| v}
-}
+} unless yjit_enabled # http://ci.rvm.jp/results/trunk-yjit@ruby-sp2-docker/4466770
 
 # Selector should be GCed (free'ed) withtou trouble
 assert_equal 'ok', %q{