docs: update release notes for 0.20

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

@@ -94,6 +94,12 @@ circuit. The indices are only available for forwarding events saved after v0.20.
     * [11](https://github.com/lightningnetwork/lnd/pull/9972)
 
 ## RPC Updates
+* Previously the `RoutingPolicy` would return the inbound fee record in its
+  `CustomRecords` field, which is duplicated info as it's already presented in
+  fields `InboundFeeBaseMsat` and `InboundFeeRateMilliMsat`. This is now
+  [fixed](https://github.com/lightningnetwork/lnd/pull/9572), the affected RPCs
+  are `SubscribeChannelGraph`, `GetChanInfo`, `GetNodeInfo` and `DescribeGraph`.
+
 
 ## lncli Updates