Add empty changelog entry (#3509)

Author: aabmass

CHANGELOG.md

@@ -9,6 +9,8 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 > The following components are released independently and maintain individual CHANGELOG files.
 > Use [this search for a list of all CHANGELOG.md files in this repo](https://github.com/search?q=repo%3Aopen-telemetry%2Fopentelemetry-python-contrib+path%3A**%2FCHANGELOG.md&type=code).
 
+## Unreleased
+
 ## Version 1.33.0/0.54b0 (2025-05-09)
 
 ### Added