@Override
		public void clearCancelled() {
			// don't allow this
		}
A monitor that allows us to make sure that this update manager does not clear the cancel
done in {@link ThreadedTableModelUpdateMgr#dispose()}.  This is useful if we want to never
again perform any work, such as when we are disposed.
Ghidra/Framework/Docking/src/main/java/docking/widgets/table/threaded/ThreadedTableModelUpdateMgr.java