release-notes: update for 0.19.0

Author: bitromortac

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

@@ -40,6 +40,12 @@
   a graceful shutdown of LND during the main chain backend sync check in certain
   cases.
 
+* [Bimodal pathfinding probability
+  improvements](https://github.com/lightningnetwork/lnd/pull/8329). A fallback
+  probability is used if the bimodal model is not applicable. Fixes are added
+  such that the probability is evaluated quicker and to be more accurate in
+  outdated scenarios.
+
 # New Features
 ## Functional Enhancements
 ## RPC Additions
@@ -154,6 +160,7 @@
 # Contributors (Alphabetical Order)
 
 * Animesh Bilthare
+* bitromortac
 * Boris Nagaev
 * CharlieZKSmith
 * Elle Mouton