Changing stream rule does not change result preview

## Expected Behavior
changed rules should be applied to the sample message

## Current Behavior
The first result is never updated, even when changing rules to match/not match

## Steps to Reproduce (for bugs)

1. Go to stream rules
2. Load a message
3. Modify rule to match/not match
4. Result doesn't change accordingly

## Context

## Your Environment

* Graylog Version: 6.0.0.rc2
* Java Version:
* OpenSearch Version:
* MongoDB Version:
* Operating System:
* Browser version: