misc: 1.4.0 changelog

Author: kamilogorek

CHANGELOG.md

@@ -24,7 +24,7 @@ A major release `N` implies the previous release `N-1` will no longer receive up
 
 - TBA
 
-# 1.4.0
+## 1.4.0
 
 - No longer set the last event id for transactions #1186
 - Added support for client reports (disabled by default for now) #1181