docs: move the /ssl mount changelog entry under 2.14.2-1

The entry added by #873 was left under "[Unreleased]" when 2.14.2-1 was
cut, although the release contains the change (config.json maps ssl
read-only at the v2.14.2-1 tag). Move it under the release heading so the
update dialog in Home Assistant no longer shows it as unreleased.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>

Author: cmatte

zigbee2mqtt/CHANGELOG.md

@@ -1,8 +1,5 @@
 ## 2.14.2-1
 - Updated Zigbee2MQTT to version [`2.14.2`](https://github.com/Koenkk/zigbee2mqtt/releases/tag/2.14.2)
-
-## [Unreleased]
-
 - Mount the Home Assistant SSL directory into the addon container read-only (`/ssl`), so certificates managed by addons such as Let's Encrypt can be used for MQTT TLS and the frontend [#835](https://github.com/zigbee2mqtt/hassio-zigbee2mqtt/issues/835)
 
 ## 2.14.1-1