Change Requests for features that were deleted fail to load and cannot be removed

[rolodato]

How are you running Flagsmith

• Self Hosted with Docker
• Self Hosted with Kubernetes
• SaaS at flagsmith.com
• Some other way (add details in description below)

Describe the bug

See reproduction steps

Steps To Reproduce

1. Create any change request for a feature
2. Delete the feature
3. Navigate to the change request you created

The change request fails to load, incorrectly says it was not found, and will never be removed from this list.

The sidebar menu will forever display a badge indicating there are open change requests.

Expected behavior

Lots of ways to improve this - at a minimum, show a correct error message and allow deleting the CR.

Screenshots

[kyle-ssg]

Fixed as part of #4852 since this migrates change requests to typescript