release-notes: update for 0.19.0

Author: Crypt-iQ

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

@@ -170,6 +170,9 @@
  use the configured budget values for HTLCs (first level sweep) in parcticular
  `--sweeper.budget.deadlinehtlcratio` and `--sweeper.budget.deadlinehtlc`.
 
+* [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