docs: update release notes

Author: ellemouton

docs/release-notes/release-notes-0.18.0.md

@@ -212,6 +212,9 @@
 * Add new [lnwire](https://github.com/lightningnetwork/lnd/pull/8044) messages 
   for the Gossip 1.75 protocol.
 
+* Add new [channeldb](https://github.com/lightningnetwork/lnd/pull/8164) types 
+  required for the Gossip 1.75 protocol.
+
 ## Testing
 
 * Added fuzz tests for [onion