docs: add tests 1.1.2 changelog entry

Author: Davide Melfi

aws-lambda-java-tests/RELEASE.CHANGELOG.md

@@ -1,3 +1,7 @@
+### March 26, 2026
+`1.1.2`:
+- Add serialization round-trip tests covering 66 event classes
+
 ### August 26, 2021
 `1.1.1`:
 - Bumped `aws-lambda-java-events` to version `3.11.0`