docs: add release notes for remote balance field

docs/release-notes/release-notes-0.15.0.md

@@ -19,6 +19,13 @@
 * [Allow disabling migrations if the database backend passed to `channeldb` was
   opened in read-only mode](https://github.com/lightningnetwork/lnd/pull/6084).
 
+## RPC Server
+
+* [Add value to the field
+  `remote_balance`](https://github.com/lightningnetwork/lnd/pull/5931) in
+  `pending_force_closing_channels` under `pendingchannels` whereas before was
+  empty(zero).
+
 ## Code Health
 
 ### Code cleanup, refactor, typo fixes