[ruby/irb] Add TODO comment to remove disabling autocomplete later

https://github.com/ruby/irb/commit/856f001b60

test/irb/yamatanooroti/test_rendering.rb

@@ -26,6 +26,7 @@ begin
     end
 
     def test_launch
+      # TODO Remove the disabling autocomplete after new versoin of reline gem is released.
       write_irbrc <<~'LINES'
         puts 'start IRB'
         IRB.conf[:USE_AUTOCOMPLETE] = false