Log Message:
devel/ruby-async: update to 2.6.4

2.6.4 (2023-08-25)

* If a task returns an exception value, do not raise it in #wait. (#270)
* Minor improvement to test performance.
* Test multiple process waits. (#273)
* Failing timeout while getting from stdin. (#266)
* Fix handling of TimeoutError in io_wait. (#274)
* Add test for blocking IO#gets in task. (#267)