Cant remove phantom sprint

Summary

It is not possible to delete phantom sprints that appear when selecting sprints. These sprints are sometimes no longer needed and a user should be able to delete them like regular sprints.

How to reproduce

1. Create a software project A
2. Create a sprint in project A
3. Create Project B
4. Delete project A
5. Now create an issue and try to link a sprint to it.

Expected behavior

Only available sprints should appear on the list

Actual results

Sprints from the deleted project appear as future sprints.

Workaround

Currently none