When running in --watch mode there are memory leak warnings

# Issues

Running the simple `example.py` with `dramatiq --watch . example` will show the following warning on file changes:

```
/home/.pyenv/versions/3.12.1/lib/python3.12/multiprocessing/resource_tracker.py:254: UserWarning: resource_tracker: There appear to be 51 leaked semaphore objects to clean up at shutdown
warnings.warn('resource_tracker: There appear to be %d '
```

## What OS are you using?

MacOS Ventura

## What version of Dramatiq are you using?

v1.15.0 (pip install)

## What did you do?

Just run the simple example

## What did you expect would happen?

No warnings about memory leaks

## What happened?

Wether using python 3.12.1 or 3.10.13 the warning is shown on restart due to file change.

Stopping the app via Ctrl-C will shutdown without any warnings