Add release notes for 2.2.0

Author: jdrew82

docs/admin/release_notes/version_2.0.md

@@ -40,3 +40,7 @@ Major release with Pydantic v2 upgrade and subsequent bug fixes.
 - @gsnider2195 made their first contribution in [PR #284](https://github.com/networktocode/diffsync/pull/284)
 - @mjbear made their first contribution in [PR #286](https://github.com/networktocode/diffsync/pull/286)
 - @jdrew82 made their first contribution in [PR #289](https://github.com/networktocode/diffsync/pull/289)
+
+## [v2.2.0] - 2025-12-08
+
+Remove Python 3.9 support as it's EOL.