testCopyFromHasWriteBackpressure() fails intermittently

### Describe the issue

The test testCopyFromHasWriteBackpressure() fails intermittently, especially in CI.

### Vapor version

x

### Operating system and version

Linux

### Swift version

6.2

### Steps to reproduce

_No response_

### Outcome

_No response_

### Additional notes

_No response_