Fix error message in save command

numbat/src/command.rs

@@ -315,7 +315,7 @@ impl<Editor> CommandRunner<Editor> {
                         parser
                             .err_through_end_from(
                                 2,
-                                "`save` requires exactly one argument, the destination",
+                                "`save` takes at most one argument (the destination, or history.nbt if omitted)",
                             )
                             .into(),
                     ));