[Memory-opti:fix leak] fix world server leak

[Alexdoru]

[OvermindDL1]

First of all, this code looks good, and is disturbing that it leaked before, good find!

The failing build is entirely unrelated, that was just failing to acquire some RFG-standard-dependencies due to a maven server being down, nothing about FMP at all and if someone who has access (not me) can rerun the task then it should run now (I just tried it locally successfully so the maven server is back up).

As an aside, it's interesting that https://files.prismlauncher.org/maven/ is a maven repo in RFG, never noticed that before. Not something you'd expect to go down though so it's probably fine, but might be good to replicate the log4j variant they have (I could put it on my maven, which basically never goes down, like an hour total in 25 years) if that's the only thing it acquires from prisms site and it could be removed? But that's conversation for another time, and probably unnecessary anyway as I wouldn't guess prisms site goes down often regardless.