Replace hsRAMStream::Truncate call with Reset to match new behavior

The previous implementation of hsRAMStream::Truncate incorrectly deleted
the entire stream data, not just starting at the current seek position.

Sources/Plasma/PubUtilLib/plNetCommon/plNetCommonHelpers.cpp

@@ -275,7 +275,7 @@ void plCreatableListHelper::Write( hsStream* s, hsResMgr* mgr )
             }
         }
 
-        ram.Truncate();
+        ram.Reset();
 
         ram.WriteByte(fFlags);
         ram.WriteLE32(bufSz);