iohub issue impacts support for MacOS and Windows

[applio]

Motivated in part by reports of not being able to use parallel execution in VisCy except on Linux (see #237), this issue is meant to track a PR opened against iohub which should enable the use of VisCy on MacOS and Windows: czbiohub-sf/iohub#346

Please see that PR and its associated issue, czbiohub-sf/iohub#345, for a better description but in short, executing VisCy with num_workers=0 currently works on multiple platforms because it disables the use of parallel processes via multiprocessing which would otherwise trigger an underlying issue in the v0.2.2 release of iohub. That PR attempts to address the issue in iohub, to VisCy's benefit.

In local testing, using VisCy with that PR's version of iohub allowed the successful parallel execution of VisCy on non-Linux systems.