Wrongly translated video instance example link

[adbenitez]

I just realized that some people have translated the string videochat_instance_example ("Example: https://your-server.org/$ROOM") translating the $ROOM parameter which should not be changed to something like:

• Príklady: https://meet.jit.si/$MIESTNOST [...]
• Voorbeeld: https://meet.jit.si/$KAMER

maybe a comment should be put on top of the line of this string clarifying that $ROOM should not be translated and maybe also check that $ROOM was not translated in some of the translations scripts we have