Windows 8.1 and 10 relays claim to be Windows 8

In Windows 8.1, Microsoft changed the behaviour of the GetVersionEx function so that it returns 6.2 (Windows 8) for applications without a compatibility manifest. (For applications with a compatibility manifest, it returns the version in that manifest.)

https://docs.microsoft.com/en-au/windows/desktop/api/sysinfoapi/nf-sysinfoapi-getversionexa

We should change the version returned by Tor's uname function to "Windows 8 or later".