Assets do not get removed from the 'Ready For' count for shot tasks when they are deleted from the project

[harywilke]

Context
Zou version: 0.20.83
Kitsu 0.20.101
Zou installation type: self-hosted

Describe the bug
Assets do not get removed from the 'Ready For' count for shot tasks when they are deleted from the project

To reproduce:

1. create a shot with a task.
2. create an asset
3. assign the asset to the shot in the breakdown page
4. delete the asset from the project.
5. check the shots page, the little gray/green dot on the task will show 0/1 when you hover over it.

Same behavior, showing 0/1, if the asset is only archived and not yet deleted.

Expected behavior
The breakdown ready count to be updated when assets are deleted.