Move python/postgres deprecation notice to the top of 1.50 changelog

Author: anoadragon453

Diff for: CHANGES.md

@@ -1,10 +1,10 @@
 Synapse 1.50.0 (2022-01-18)
 ===========================
 
-No significant changes since 1.50.0rc2.
-
 Please note that we now only support Python 3.7+ and PostgreSQL 10+ (if applicable), because Python 3.6 and PostgreSQL 9.6 have reached end-of-life.
 
+No significant changes since 1.50.0rc2.
+
 
 Synapse 1.50.0rc2 (2022-01-14)
 ==============================