Add Python 3.10 to unit test matrix

[ryantwolf]

Description

Adds Python 3.10 to the CPU unit test matrix.

Usage

N/A

Checklist

• I am familiar with the Contributing Guide.
• New or Existing tests cover these changes.
• The documentation is up to date with these changes.

[ryantwolf]

Sorry @ayushdg I didn't realize it was this easy to add a different Python version to our tests. If I had known I would've done it in the original PR.

[ayushdg]

No worries. It can lead to higher waiting times for tests to complete, but in our matrix isn't too complex and should be fine for now.