Update CHANGELOG

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CHANGELOG

 Please view this file on the master branch, on stable branches it's out of date.
 
-v 8.4.0 (unreleased)
-  - Add support for Google reCAPTCHA in user registration to prevent spammers (Stan Hu)
-  - Implement new UI for group page
-  - Implement search inside emoji picker
-  - Add API support for looking up a user by username (Stan Hu)
-  - Add project permissions to all project API endpoints (Stan Hu)
-  - Only allow group/project members to mention `@all`
-  - Expose Git's version in the admin area
-  - Add "Frequently used" category to emoji picker
-  - Add CAS support (tduehr)
-  - Add link to merge request on build detail page.
-  - Revert back upvote and downvote button to the issue and MR pages
-
-v 8.3.2 (unreleased)
+v 8.3.2
   - Disable --follow in `git log` to avoid loading duplicate commit data in infinite scroll (Stan Hu)
-  - Enable "Add key" button when user fills in a proper key
+  - Add support for Google reCAPTCHA in user registration
 
 v 8.3.1
   - Fix Error 500 when global milestones have slashes (Stan Hu)