Unclear warning message when leaving room as last user

[montaropdf](https://matrix.to/#/@montaropdf:matrix.org) sent this feedback into [#element-translations:matrix.org](https://matrix.to/#/#element-translations:matrix.org).

> Hello,
>
> I would like to report that the text displayed when the last user (admin?) of a room left it, it is not clear about what will happens to the room.
>
> In french and english, it is istated that the room will not be joinable anymore, however, I have understood that in fact the romm is deleted. Moreover, the german version seems closer to the reality.
>
> Hence, would it be possible to adapt the warning message, to state clearly what will happen to the room, in the situation described above, for all languages?

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