Clean up "remove/change this after the game is over" comments

**What needs to be cleaned up?**
There are a bunch of comments, mostly on various properties, that say something like "remove/change this after the current multiplayer game is over to avoid breaking savegames". Some of them are pretty old. Once the current games are over, go through and clean them up.

**How will this benefit us?**
Cleaner code, no unneeded data in savegames

**What potential drawbacks are there to making this change?**
Breaking savegames if doing it too soon?

**Related issues**
N/A