fix wrong ref in changelog

CHANGELOG.md

@@ -5,7 +5,7 @@
 - query autoritative nameserver to bypass DNS cache
   ([#424](https://github.com/deltachat/chatmail/pull/424))
 
-- add mtail support (new optional `mail_address` ini value)
+- add mtail support (new optional `mtail_address` ini value)
   This defines the address on which [`mtail`](https://google.github.io/mtail/)
   exposes its metrics collected from the logs.
   If you want to collect the metrics with Prometheus,