bug: remove unused "Django migr" button

[evemartin]

Describe the bug
In the Level Editor Map tab, some users have an extra unused "Django migr" button. This doesn't do anything anymore and should be removed

To Reproduce
Steps to reproduce the behaviour:

1. Log in locally as Albert Einstein (alberteinstein@codeforlife.com)
2. Go to the Level Editor
3. On the Map tab, you should see a button saying "Django migr"

Expected behaviour
The "Django migr" button should not be there

Screenshots

[razvan-pro]

Sorry, I just came across this 😅 As far as I remember, this button is only visible by admins and it's used to create new levels - it will copy the code that can then be pasted in the repo somewhere (I can't remember exactly where, I assume it will be a migration that will insert the level in the database).