Fix an obvious memory leak.

This thing was pissing me off, which made me piss off a lot of other people,
which pissed off even more people, so the entire planet got pissed off and
nuclear warfare began. So, let's not do stupid crap and piss me off, okay?

Sources/Plasma/PubUtilLib/plPhysX/plSimulationMgr.cpp

@@ -358,7 +358,6 @@ void plSimulationMgr::Init()
     if (gTheInstance->InitSimulation())
     {
         gTheInstance->RegisterAs(kSimulationMgr_KEY);
-        gTheInstance->GetKey()->RefObject();
         plgDispatch::Dispatch()->RegisterForExactType(plAgeLoadedMsg::Index(), gTheInstance->GetKey());
     }
     else
@@ -376,11 +375,8 @@ void plSimulationMgr::Shutdown()
     hsAssert(gTheInstance, "Simulation manager missing during shutdown.");
     if (gTheInstance)
     {
-        // UnRef to match our Ref in Init(). Unless something strange is
-        // going on, this should destroy the instance and set gTheInstance to nil.
-//      gTheInstance->GetKey()->UnRefObject();
         plgDispatch::Dispatch()->UnRegisterForExactType(plAgeLoadedMsg::Index(), gTheInstance->GetKey());
-        gTheInstance->UnRegister();     // this will destroy the instance
+        gTheInstance->UnRegisterAs(kSimulationMgr_KEY);     // this will destroy the instance
         gTheInstance = nil;
     }
 }