Include changes since RC1 in release notes for 5.3 GA

Issue: #1541

Author: sbrannen

documentation/src/docs/asciidoc/release-notes/release-notes-5.3.0.adoc

@@ -121,6 +121,21 @@ repository on GitHub.
     many tests as possible while still informing the user of containers and tests that
     could not be properly discovered.
 
+==== Bug Fixes since 5.3 RC1
+
+* The `junit-jupiter-params` JAR file was missing the required Kotlin metadata for the
+  `getAs<Class>(index)` Kotlin extension method. The underlying packaging issue has been
+  solved, and the extension method has been renamed to `get<Class>(index)` as originally
+  intended in 5.3.0-M1.
+* `TestInstanceFactory` extensions are properly _inherited_ within `@Nested` test class
+  hierarchies.
+
+==== Breaking Changes since 5.3 RC1
+
+* `@Nested` test classes can no longer _override_ `TestInstanceFactory` extensions
+  registered on an _enclosing_ class. This aligns with the behavior for
+  `TestInstanceFactory` extensions registered within a conventional test class hierarchy.
+
 ==== New Features and Improvements
 
 * Experimental support for parallel test execution. By default, tests are still executed