add deprecation warning for mempoolfullrbf

src/node/mempool_args.cpp

@@ -93,6 +93,9 @@ util::Result<void> ApplyArgsManOptions(const ArgsManager& argsman, const CChainP
     }
 
     mempool_opts.full_rbf = argsman.GetBoolArg("-mempoolfullrbf", mempool_opts.full_rbf);
+    if (!mempool_opts.full_rbf) {
+        LogInfo("Warning: mempoolfullrbf=0 set but deprecated and will be removed in a future release\n");
+    }
 
     mempool_opts.persist_v1_dat = argsman.GetBoolArg("-persistmempoolv1", mempool_opts.persist_v1_dat);