Publish a PyPy3.9-compatible wheel

[edgarrmondragon]

The latest PyPy wheel supports versions 3.6-3.8, but not 3.9

[nedbat]

The PyPy wheel now installs on 3.7, 3.8, and 3.9, as of 5c5caa2.

[edgarrmondragon]

Thanks @nedbat!

[nedbat]

This is now released as part of coverage 7.0.1.