Fix typo in Javadoc (#1749)

Change "root root" to "root node".
diff --git a/elasticjob-lite/elasticjob-lite-core/src/main/java/org/apache/shardingsphere/elasticjob/lite/internal/storage/JobNodeStorage.java b/elasticjob-lite/elasticjob-lite-core/src/main/java/org/apache/shardingsphere/elasticjob/lite/internal/storage/JobNodeStorage.java
index 63e8eef..6893322 100644
--- a/elasticjob-lite/elasticjob-lite-core/src/main/java/org/apache/shardingsphere/elasticjob/lite/internal/storage/JobNodeStorage.java
+++ b/elasticjob-lite/elasticjob-lite-core/src/main/java/org/apache/shardingsphere/elasticjob/lite/internal/storage/JobNodeStorage.java
@@ -109,7 +109,7 @@
     /**
      * Create job node if needed.
      * 
-     * <p>Do not create node if root root not existed, which means job is shutdown.</p>
+     * <p>Do not create node if root node not existed, which means job is shutdown.</p>
      * 
      * @param node node
      */