Fix wrong result for TopN when removing records out of TopN

@Test
public void testCornerCase2() throws Exception {
	AbstractTopNFunction func = createFunction(RankType.ROW_NUMBER, new ConstantRankRange(1, 2), false,
				false);
	OneInputStreamOperatorTestHarness<RowData, RowData> testHarness = createTestHarness(func);
	testHarness.open();
	testHarness.processElement(insertRecord("a", 1L, 1));
	testHarness.processElement(insertRecord("a", 2L, 2));
	testHarness.processElement(insertRecord("a", 3L, 2));
	testHarness.processElement(insertRecord("a", 4L, 4));
	testHarness.processElement(insertRecord("a", 5L, 4));

	testHarness.processElement(deleteRecord("a", 4L, 4));
	testHarness.processElement(deleteRecord("a", 1L, 1));
	testHarness.processElement(deleteRecord("a", 2L, 2));
	testHarness.close();

	List<Object> expectedOutput = new ArrayList<>();
	expectedOutput.add(insertRecord("a", 1L, 1));
	expectedOutput.add(insertRecord("a", 2L, 2));
	expectedOutput.add(deleteRecord("a", 1L, 1));
	expectedOutput.add(insertRecord("a", 3L, 2));
	expectedOutput.add(deleteRecord("a", 2L, 2));
	expectedOutput.add(insertRecord("a", 5L, 4));
	assertorWithRowNumber.assertOutputEquals("output wrong.", expectedOutput, testHarness.getOutput());
}