Boost number of makeinstancesufo pool processors by one

[skef]

Description

The makeinstancesufo tests currently fail on single-processor systems due to requesting 0 cores for the multiprocessing pool. This bumps the count by one.

The motivation to leave one processor free is understandable. However, if the "organizing" thread isn't very active when the pool is running it seems fine to rely on the timesharing in the OS and just use all the cores.

Checklist:

• I have followed the Contribution Guidelines
• I have added test code and data to prove that my code functions correctly
• I have verified that new and existing tests pass locally with my changes
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation

[josh-hadley]

I approved this and OK'd @skef to bypass the check requirements because of some weirdness with re-triggering the required actions. They ran and passed on the skef/afdko branch so I'm satisfied that everything is 🆗