RJIT: Skip a flaky test_thread test for now

and unskip a ractor test that was actually running

bootstraptest/test_ractor.rb

@@ -283,8 +283,7 @@ assert_equal 30.times.map { 'ok' }.to_s, %q{
   30.times.map{|i|
     test i
   }
-} unless ENV['RUN_OPTS'] =~ /--rjit-call-threshold=5/ || # This always fails with --rjit-wait --rjit-call-threshold=5
-  (ENV.key?('TRAVIS') && ENV['TRAVIS_CPU_ARCH'] == 'arm64') # https://bugs.ruby-lang.org/issues/17878
+} unless (ENV.key?('TRAVIS') && ENV['TRAVIS_CPU_ARCH'] == 'arm64') # https://bugs.ruby-lang.org/issues/17878
 
 # Exception for empty select
 assert_match /specify at least one ractor/, %q{

bootstraptest/test_thread.rb

@@ -483,7 +483,7 @@ assert_equal 'foo', %q{
   [th1, th2].each {|t| t.join }
   GC.start
   f.call.source
-}
+} unless ENV['RUN_OPTS'] =~ /rjit/ # flaky
 assert_normal_exit %q{
   class C
     def inspect