Log Message:
devel/ruby-async: update to 2.6.3

2.6.3 (2023-07-28)

*  Documentation improvements. (#248)
* Modernize gem. (#249)
* Extended documentation. (#250)
  - Consistent usage of reactor/event loop terminology.
  - Show how to use `ensure` with barrier.
  - Expanded documentation / questions / answers.
  - Add best practices.
* Improve readme.
* Add code of conduct.
* Replace 3.times do with 1.upto(3) do.
* Fix guide lines, fixes #251.
* Fix Markdown syntax highlighting marker (#252)
* Guide: ensure barrier is in scope (#253)
  - This change avoids a NoMethodError on the barrier local variable.  And
    also a LoadError, with the Async::Barrier constant.
* Follow-up barrier in scope docs fix (#254)
  - This makes the same change as #253 but in this file.
* Don't run scheduler when there is a pending exception. (#262)
* Ensure the scheduler is cleaned up on exit.
* Better handling of interrupted flag. (#264)