Update "Known Issues" in README

[mpguerra]

There's a few things that we should update in the "Known issues" section of the README:

1. We should remove the line about not having Windows support

No Windows support #3801. We used to test with Windows Server 2019, but not any more; see the issue for details.

2. We should update the latest regarding arti

Experimental Tor support is disabled until #5492. This happened due to a Rust dependency conflict, which could only be resolved by arti upgrading to a version of x25519-dalek with the dependency fix.

There maybe other content that needs to be updated also since we restored Windows support.

depends-on: #8320