Fix M4 output

[rzuckerm]

Description

I forgot to add the number of threads to the output.

Contributing requirements

• I read the contribution guidelines in CONTRIBUTING.md.
• I placed my solution in the correct solution folder.
• I added a README.md with the right badge(s).
• I added a Dockerfile that builds and runs my solution.
• I selected drag-race as the target branch.
• All code herein is licensed compatible with BSD-3.

[rbergen]

Your last commit fixed one thing and broke another. I've added concrete suggestions for the correct format, below. If you're not on the "new PR experience" in GitHub you can add them to one commit from the "Files changed" tab.

[rbergen]

LGTM