Update TortoiseHareAlgo.java

Added {} after if statement instead of directly writing statement

Author: TejasSingh022

src/main/java/com/thealgorithms/datastructures/lists/TortoiseHareAlgo.java

@@ -31,7 +31,9 @@ public void append(E value) {
     }
 
     public E getMiddle() {
-        if (head == null) return null;
+        if (head == null){
+            return null;
+        }
 
         Node<E> slow = head;
         Node<E> fast = head;