docs: mark platformP2PPort and platformHTTPPort as deprecated

Author: kwvg

doc/release-notes-6811.md

@@ -0,0 +1,8 @@
+Updated RPCs
+------------
+
+* The keys `platformP2PPort` and `platformHTTPPort` have been deprecated for the following RPCs, `decoderawtransaction`,
+  `decodepsbt`, `getblock`, `getrawtransaction`, `gettransaction`, `masternode status` (only the `dmnState` key),
+  `protx diff`, `protx listdiff` and has been replaced with the key `addresses`.
+  * The deprecated key is still available without additional runtime arguments but is liable to be removed in future versions
+    of Dash Core.