Refactor RPCMode enum and checks

modules/gdscript/gdscript_function.cpp

@@ -1455,7 +1455,7 @@ GDScriptFunction::GDScriptFunction() :
 
 	_stack_size = 0;
 	_call_size = 0;
-	rpc_mode = ScriptInstance::RPC_MODE_DISABLED;
+	rpc_mode = MultiplayerAPI::RPC_MODE_DISABLED;
 	name = "<anonymous>";
 #ifdef DEBUG_ENABLED
 	_func_cname = NULL;