TB sends OS info in user agent header

I understand that you cannot prevent JS from finding out your OS. I still think we should make that as hard as possible, but it's OK for me, as I'm in safest mode most of the time anyways (unless I'm browsing the Tor Project's gitlab sigh). It would also probably be a lot of work.

However there is no reason for TB to send identifying information in strictest mode. I cite from https://blog.torproject.org/browser-fingerprinting-introduction-and-challenges-ahead/:

the approach chosen by Tor developers is simple: all Tor users should have the exact same fingerprint

While not perfectly possible, I'd like to advocate the spirit. Imagine being the only registered user on a small forum using Tor on MacOS. You leave an anonymous post on the forum, but the operator can deduce it's likely tied to your account. Every bit of identifying information halves the set of suspects, so we should minimize it wherever possible. I don't see anyone complaining about this, and I only discovered this change in TB behavior by chance, so I assume a lot of people are still operating under the assumption that their OS is not tracked.

Please fully spoof the user agent header in strictest mode and put a warning that the OS will be exposed in the description of the other modes.