Do not show confirm dialog when saving event notification. `6.0`

[linuspahl]

Please note, this is a backport of https://github.com/Graylog2/graylog2-server/pull/19073 for 6.0

Description

Motivation and Context

Before this change, when you create or update an event notification, you will see the following confirm dialog on submit.

This PR is fixing the bug by implementing a fix similar to https://github.com/Graylog2/graylog2-server/pull/18880

Please keep in mind while testing, that the confirm dialog is not showing up in development mode, by default.