for/travelers: fix typo in "Träwelling"

just happened to look at the for travellers page as i saw it linked on fedi somewhere, and was delighted to see Träwelling on there too. unfortunately there is a small typo in the name -- they spell themselves with two l.

this needs to be updated in translations too, but i have no clue what's the correct approach for doing so -- maybe just changing it here is already enough for it to get updated everywhere as it's a new text :)