Log Message:
devel/ruby-backports: update to 3.20.2

3.20.2 (2021-01-27)

* Fix a typo
* Namespace explicitly, but not Ractor
* Don't stop at ractor tests
* Tweak Ractor#inspect
* Ractor: implementation under Backports namespace
* Tweak for 2.2-
* Move filtered_queue
* Add magic constant
* Move backports dependencies out of `ractor/`; use RubyNext if need be