[Python-buildbots] Windows 8.1 worker (bolen-worker8) retirement

[David Bolen]

My Windows 8.1 worker got hit on Wednesday by some "encrypt the world"
ransomware.  I'm not quite sure the path by which it reached the Azure VM,
but regardless, it's toast.

I don't think I see enough value in re-installation, given the existence of
the Windows 10 worker, plus I can probably bump some Windows 10 worker
resources with the budget freed up by Windows 8.  So I'm planning on
letting the Windows 8 worker end its run at this point.

-- David