docs: update release notes

docs/release-notes/release-notes-0.16.0.md

@@ -122,6 +122,9 @@ https://github.com/lightningnetwork/lnd/pull/6963/)
 * [Stop sending a synchronizing error on the wire when out of
   sync](https://github.com/lightningnetwork/lnd/pull/7039).
 
+* [Update cert module](https://github.com/lightningnetwork/lnd/pull/6573) to
+  allow a way to update the tls certificate without restarting lnd.
+
 ## `lncli`
 * [Add an `insecure` flag to skip tls auth as well as a `metadata` string slice
   flag](https://github.com/lightningnetwork/lnd/pull/6818) that allows the