Update ruby-i18n to 1.8.3.
1.8.3 (2020-06-05)
Features / Improvements
* Memory and speed improvements - #527+ #528
* Add option to disable fallbacks for I18n.exists? check - #482
* Add an on_fallback hook to allow users to be notified when a fallback
happens - #520
Bug Fixes
* Fix an issue with deep_merge and chain fallback backends - #499 & #509
* Fix an issue with Rails ordinal number proc and keyword splatting - #521
* Pass options as keyword arguments to translation procs - #529
* Fix pluralize on unknown locale with attributes - #519
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