Require less strict `speedy` version

[maxded]

Checklist

• [x] I have read the Contributor Guide
• [x] I have read and agree to the Code of Conduct
• [x] I have added a description of my changes and why I'd like them included in the section below

Description of Changes

Due to some internal dependency clashes, I want to downgrade the minimum requirement of the speedy dependency. Any top-level user can still specify to use 0.8.6 as that is a non-breaking change.