[Bug] Potential memory leak issue

[jhqwqmc]

Pre-Issue Checklist

• I have checked that I am on the latest version of Terra.
• I have searched the github issue tracker for similar issues, including
  closed ones.
• I have made sure that this is not a bug with another mod or plugin, and it
  is Terra that is causing the issue.
• I have checked that this is an issue with Terra and not an issue with the
  pack I am using.
• I have attached a copy of the latest.log file
• I have filled out and provided all the appropriate information.

Environment

Name	Value
Terra Version	6.6.6-BETA+451683aff
Platform / Platform Version	Paper
Any External Plugins or Mods	Terra spark
Terra Packs In Use	None
Terra Addons In Use	None

Issue Description

Frequently loading and unloading different worlds

Steps to reproduce

1. Load a world that has not been loaded before
2. Unload the world
3. Repeat steps 1 to 2

Expected behavior

World objects can be normally reclaimed.

Actual behavior

Terra/platforms/bukkit/nms/src/main/java/com/dfsek/terra/bukkit/nms/NMSInjectListener.java

Line 25 in c6eb2f4

private static final Set<World> INJECTED = new HashSet<>();

The world is added to this Set during initialisation and remains there after unloading, preventing its removal and thus hindering its reclaiming.

Full stacktrace

None

Additional details

None

[MistakingManx]

Bump.

I'm glad someone actually went through the code to find the issue for them. I had a really similar oversight in a lot of my older JavaScript programs, it's neat to know that it happens to everyone and I'm not just dumb.