webxdc status updates not processed in mailing lists

[adbenitez]

in recent versions of delta chat, it has been noticed that it is no longer possible to receive status updates of webxdc apps in mailing lists, if you play some game, you can see your status updates being sent, but they don't arrive or more precisely it seems core is discarding them for some reason, it used to work in the past

• Operating System (Linux/Mac/Windows/iOS/Android): Android
• Delta Chat Version: latest
• Expected behavior: can play games with shared scoreboards in mailing lists
• Actual behavior: only your own status updates are visible to you
• Steps to reproduce the problem: send a webxdc game with shared scoreboard in an anonymous mailing list like the ones listed in the super groups bot, see https://delta.chat/en/contribute

[link2xt]

Likely broken by this change: #3568

We can try to explicitly allow mailing lists.

[link2xt]

Closed on stable branch with #4563.