Suppress unused return value ErrorProne on siftUp

This tells ErrorProne not to fret in this case.
Caught this while porting code to google3 to get it running with tsan.

Flag: EXEMPT lil' touch-up

Change-Id: Idedee92421a22a885c6470812db6b7219ae83465

parent dc33f8b1

core/java/android/os/MessageHeap.java

+3 −1

Original line number	Diff line number	Diff line
		@@ -165,7 +165,9 @@ public final class MessageHeap {
		m.heapIndex = i;
		mHeap[i] = m;

		siftUp(i);
		// We sift up to ensure that the heap invariant is maintained,
		// but we don't care whether the message was actually moved.
		boolean unused = siftUp(i);
		}

		public void maybeShrink() {