Tab fix

exercises/series/src/test/java/SeriesTest.java

     public void canSliceByOne() {
         Series series = new Series("01234");
         List<List<Integer>> expected = Arrays.asList(
-		        Collections.singletonList(0),
+		Collections.singletonList(0),
                 Collections.singletonList(1),
                 Collections.singletonList(2),
                 Collections.singletonList(3),