fix typo in WordCount

Author: James Lee

src/main/java/com/sparkTutorial/rdd/WorldCount.java renamed to src/main/java/com/sparkTutorial/rdd/WordCount.java

@@ -10,7 +10,7 @@
 import java.util.Arrays;
 import java.util.Map;
 
-public class WorldCount {
+public class WordCount {
 
     public static void main(String[] args) throws Exception {