If you disable "Support PointLight WholeSceneShadows" spotlights stop casting shadows. This is working as expected in 4.20 CL# 4369336.
Found in 4.21 CL# 4753647 and 4.22 CL# 4809892
This is a regression.
Results:
No shadows will be produced from the cube
Expected:
A shadow would be cast 
There's no existing public thread on this issue, so head over to Questions & Answers just mention UE-69344 in the post.
| 0 | 
| Component | UE - Graphics Features | 
|---|---|
| Affects Versions | 4.21, 4.22 | 
| Target Fix | 4.22 | 
| Created | Jan 30, 2019 | 
|---|---|
| Resolved | Jan 31, 2019 | 
| Updated | Jun 11, 2019 |