chore: add changelog entry

Signed-off-by: florian <[email protected]>

Author: florianvazelle

CHANGELOG.md

@@ -9,6 +9,7 @@ Inspired from [Keep a Changelog](https://keepachangelog.com/en/1.0.0/)
 - Updated opensearch-py APIs to reflect [opensearch-api-specification@578a78d](https://github.com/opensearch-project/opensearch-api-specification/commit/578a78dcec746e81da88f81ad442ab1836db7694)
 ### Changed
 - Rename `DenseVector` field type to `KnnVector` ([925](https://github.com/opensearch-project/opensearch-py/pull/925))
+- Migrate `setup.py` to a `pyproject.toml` ([951](https://github.com/opensearch-project/opensearch-py/pull/951))
 ### Deprecated
 ### Removed
 ### Fixed