Trying to delete a shared dashboard shows contradicting results

## Expected Behavior
Delete should either be unavailable or display the correct message

## Current Behavior
When trying to delete a shared dashboard which I am not owner of, I get the following messages (plus a short flickering screen showing the party gorilla, probably for the subconsciousness)

## Possible Solution
only show error message or disable delete button

## Steps to Reproduce (for bugs)
1. Share a dashboard with another user (not as owner)
2. Log in as that user
3. Try to delete the dashboard

## Context

## Your Environment

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