doc: add release note about removal of deprecatedrpc=fees flag

Author: theStack

doc/release-notes.md

@@ -62,6 +62,13 @@ Updated RPCs
   change that behaviour. Excluding coinbases was previously deprecated in 23.0.
   (#25171)
 
+- The `deprecatedrpc=fees` configuration option has been removed. The top-level
+  fee fields `fee`, `modifiedfee`, `ancestorfees` and `descendantfees` are no
+  longer returned by RPCs `getmempoolentry`, `getrawmempool(verbose=true)`,
+  `getmempoolancestors(verbose=true)` and `getmempooldescendants(verbose=true)`.
+  The same fee fields can be accessed through the `fees` object in the result.
+  The top-level fee fields were previously deprecated in 23.0. (#25204)
+
 Changes to wallet related RPCs can be found in the Wallet section below.
 
 New RPCs