Review release scripts and policies

Hi,

This is a recommendation to:

- Create a release on GitHub for [v6.2.1](https://github.com/keybase/client/commit/e6160f1b9ed77eb43d214f5fb1d56ce390d6eed9) indicating that it comes with a Windows release, in accordance with the current contents of [`update-windows-prod-v2.json`](https://s3.amazonaws.com/prerelease.keybase.io/update-windows-prod-v2.json)
- Adding information to the [GitHub v6.2.2 release](https://github.com/keybase/client/releases/tag/v6.2.2) indicating whether it will be released on Windows as well
- Adjust [`update-windows-prod-v2.json`](https://s3.amazonaws.com/prerelease.keybase.io/update-windows-prod-v2.json) so that it reflects v6.2.2 if there is a Windows release

I am a volunteer in charge of the [Chocolatey installer for keybase](https://community.chocolatey.org/packages/keybase/6.2.1). In my work I keep an eye on `update-windows-prod-v2.json`. I already published v6.2.1 based on the updates to the `json`. This GitHub issue aims to make it clear to keybase and Chocolatey users as to which platforms v6.2.2 is published on.

This brings v6.2.2 to the tradition seen in the other GitHub releases, which specify which platforms are getting the release.

Thanks, and keep up the good work!

Start by checking the linked GitHub v6.2.1 and v6.2.2 release pages alongside update-windows-prod-v2.json. Verify whether v6.2.2 includes a Windows release, then update the release information and JSON consistently; done means the platform status is clear on GitHub and reflected in the JSON used by the Chocolatey installer.

Written by the indexing model from the issue text.