Add missing newline at end of TopologicalSort class

Author: the-yash-rajput

src/main/java/com/thealgorithms/graph/TopologicalSort.java

@@ -120,3 +120,4 @@ public static List<Integer> sort(Graph g) {
         return ans;
     }
 }
+

src/test/java/com/thealgorithms/graph/TopologicalSortTest.java

@@ -335,3 +335,4 @@ void testCycleDetection() {
         assertEquals("cycle detected in graph", exception.getMessage());
     }
 }
+