Editting an "out of the box" plugin/boefje results in a 404 error

[TwistMeister]

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Describe the bug
When editing a boefje variant that's present out of the box you'll get an error (404) after saving. Probably introduced in branch #3521

To Reproduce
Steps to reproduce the behavior:

1. Go to 'boefje detail page'
2. Click on 'edit variant' on an existing variant
3. Scroll down to the bottom of the form and submit
4. See 404 error

Expected behavior
The boefje variant should be updated with any changes made in the form

Screenshots

Screen.Recording.2024-09-26.at.14.25.40.mov