MAPREDUCE-7255. Fix typo in MapReduce documentaion example (#1793)

(cherry picked from commit b343e1533b1f4ebbbf10b063c35d79d53a741321)

hadoop-mapreduce-project/hadoop-mapreduce-client/hadoop-mapreduce-client-core/src/site/markdown/MapReduceTutorial.md

@@ -1091,7 +1091,7 @@ Sure enough, the output:
     goodbye 1
     hadoop 2
     hello 2
-    horld 2
+    world 2
 
 #### Highlights