Add v5.3.0 to CHANGELOG

(cherry picked from commit 3303872)

Author: kategengler

CHANGELOG.md

@@ -1,12 +1,8 @@
 # Ember Changelog
 
-## v5.3.0-beta.2 (August 28, 2023)
+## v5.3.0 (September 18, 2023)
 
-- [#20524](https://github.com/emberjs/ember.js/pull/20524) [BUGFIX] Add url to `deprecate-implicit-route-model` deprecation
-
-## v5.3.0-beta.1 (August 7, 2023)
-
-- [#20376](https://github.com/emberjs/ember.js/pull/20376) [DEPRECATION] Deprecate implicit record loading in Ember Route per [RFC #774](https://rfcs.emberjs.com/id/0774-implicit-record-route-loading).
+- [#20376](https://github.com/emberjs/ember.js/pull/20376) / [#20524](https://github.com/emberjs/ember.js/pull/20524) [DEPRECATION] Deprecate implicit record loading in Ember Route per [RFC #774](https://rfcs.emberjs.com/id/0774-implicit-record-route-loading).
 
 ## v5.2.0 (August 7, 2023)