Positional Parameters in route_to_stream() rejected by Rule editor

When editing a rule containing `route_to_stream` seemingly valid positional parameters are rejected by the rule editor and won't allow saving.

## Expected Behavior

I would expect (according to the rule reference doc) that `route_to_stream("Some Stream",true);` work the same as:
```
route_to_stream(
name: "Some Stream",
remove_from_default: true
);
```

## Current Behavior

`route_to_stream("Some Stream",true);` is rejected by the pipeline rule editor.

## Possible Solution

No idea. Sorry.

## Steps to Reproduce (for bugs)

1. Copy and paste the above two scenarios within an otherwise valid rule.
2.
3.
4.

## Context

It may cause erroneous troubleshooting.

## Your Environment

Testing on multiple versions of Graylog 4.0 (4.02-1, 4.03, 4.05), multiple browsers and multiple OS.

Discovered by a training student during class at Graylog Academy.

* Graylog Version:
* Java Version:
* Elasticsearch Version:
* MongoDB Version:
* Operating System:
* Browser version: