meta: set title back to unreleased in changelog

Author: mitsuhiko

CHANGELOG.md

@@ -20,7 +20,7 @@ sentry-sdk==0.10.1
 
 A major release `N` implies the previous release `N-1` will no longer receive updates. We generally do not backport bugfixes to older versions unless they are security relevant. However, feel free to ask for backports of specific commits on the bugtracker.
 
-## 1.4.2
+## Unreleased
 
 - Made envelope modifications in the HTTP transport non observable #1206