Team: Remove role min required admins in readonly & creation mode

[manuelmeister]

#3348 (comment)
On the teams page (https://dev.ecamp3.ch/camps/6973c230d6b1/Harry-Potter-Lager/collaborators)

Let it be in the edit mode, as it is good to know general requirements.

TODO:

• Remove the hint that at least one manager must remain in the camp below the role dropdown in the create and in the edit dialog. (This may be the same code)
• The hint is still displayed as a tooltip when the user tries to change the role of the last manager.

[carlobeltrame]

If it's easier, it can also be removed from edit view. We have the tooltip which shows this exact message again when it's really relevant. It's not really a surprising rule, and users can easily figure out how to work around it as soon as they see the explanation.

[MarcoAllenspach]

Is it correct that just this:

this sentence must be removed (on invite people and edit people)

I will do it :)