docs: update release notes

Author: ellemouton

docs/release-notes/release-notes-0.19.0.md

@@ -239,6 +239,9 @@ The underlying functionality between those two options remain the same.
 * [Golang was updated to
   `v1.22.11`](https://github.com/lightningnetwork/lnd/pull/9462). 
 
+* Various refactors to simplify the 
+  `graph.Builder` [1](https://github.com/lightningnetwork/lnd/pull/9476).
+
 ## Breaking Changes
 ## Performance Improvements