Fix that teamless users were not listed

[fm3]

Fixes regression from #7646 – I hadn’t been aware that users without teams were even allowed… I think this double left join here now should not cause new fanout duplicates since there is only one team per user_team_role

URL of deployed dev instance (used for testing):

• https://listteamlessusers.webknossos.xyz

Steps to test:

• Remove all team memberships from a user
• They should still be listed in api/users

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• Updated changelog

[fm3]

@normanrz maybe you could have a look at this? :)