Remove forum link from weblate.sd.o

[rocodes]

Not sure if this is the right place to file this since it's more of a weblate/il8n issue, but: weblate.securedrop.org still links out to our now-defunct forum (last link in "Other SD resources") - we should remove that link, and/or decide where to direct translator discussions in conjunction with localization lab/ @cfm (maybe it's already decided and I'm out of the loop).

[eloquence]

It seems a bit tricky to edit (have to go through Django admin) but I was able to remove the dead forum link, happy to put in anything else there.