release-notes: update for 0.19.0

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

@@ -196,6 +196,9 @@
   blockbeat dispatcher is now also [taken into
   consideration](https://github.com/lightningnetwork/lnd/pull/9501).
   
+* [The server](https://github.com/lightningnetwork/lnd/pull/9458) now allocates
+ restricted slots for certain peers. This is configured by --num-restricted-slots.
+
 ## RPC Updates
 
 * Some RPCs that previously just returned an empty response message now at least