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

Author: sergeioff

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

@@ -1097,7 +1097,7 @@ Sure enough, the output:
     goodbye 1
     hadoop 2
     hello 2
-    horld 2
+    world 2
 
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