docs: update release notes

Author: yyforyongyu

docs/release-notes/release-notes-0.20.0.md

@@ -70,6 +70,13 @@ circuit. The indices are only available for forwarding events saved after v0.20.
   finish under this timeout value. Consider using a larger timeout value if you
   have a slow network.
 
+* A [new config](https://github.com/lightningnetwork/lnd/pull/10102) value
+  `gossip.peer-msg-rate-bytes=102400` is introduced to allow limiting the
+  outgoing bandwidth used by each peer when processing gossip-related messages.
+  Note this is different from `gossip.msg-rate-bytes`, as this new config
+  controls the bandwidth per peer, while `msg-rate-bytes` controls the gossip as
+  a whole. This new config prevents a single misbehaving peer from using up all
+  the bandwidth.
 
 ## lncli Additions