chore: Add changelog entry for THIRD_PARTY_NOTICES.md

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: markushi

CHANGELOG.md

@@ -1,5 +1,11 @@
 # Changelog
 
+## Unreleased
+
+### Various fixes & improvements
+
+- chore: Add THIRD_PARTY_NOTICES.md for vendored third-party code ([#5186](https://github.com/getsentry/sentry-java/pull/5186))
+
 ## 8.34.1
 
 ### Fixes