rpc: fix getpeerinfo RPCResult mapped_as type

and mention it is only available if the asmap config flag is set.

src/rpc/net.cpp

@@ -86,7 +86,8 @@ static UniValue getpeerinfo(const JSONRPCRequest& request)
                             {RPCResult::Type::STR, "addr", "(host:port) The IP address and port of the peer"},
                             {RPCResult::Type::STR, "addrbind", "(ip:port) Bind address of the connection to the peer"},
                             {RPCResult::Type::STR, "addrlocal", "(ip:port) Local address as reported by the peer"},
-                            {RPCResult::Type::STR, "mapped_as", "The AS in the BGP route to the peer used for diversifying peer selection"},
+                            {RPCResult::Type::NUM, "mapped_as", "The AS in the BGP route to the peer used for diversifying\n"
+                                                                "peer selection (only available if the asmap config flag is set)"},
                             {RPCResult::Type::STR_HEX, "services", "The services offered"},
                             {RPCResult::Type::ARR, "servicesnames", "the services offered, in human-readable form",
                             {