MAPREDUCE-7258. HistoryServerRest.html#Task_Counters_API, modify the jobTaskCounters's itemName from taskcounterGroup to taskCounterGroup (#1808)

Co-authored-by: chenjuanni <chenjuanni@inspur.com>
Signed-off-by: Akira Ajisaka <aajisaka@apache.org>

hadoop-mapreduce-project/hadoop-mapreduce-client/hadoop-mapreduce-client-hs/src/site/markdown/HistoryServerRest.md

@@ -1415,7 +1415,7 @@ With the task counters API, you can object a collection of resources that repres
 | Item | Data Type | Description |
 |:---- |:---- |:---- |
 | id | string | The task id |
-| taskcounterGroup | array of counterGroup objects(JSON)/zero or more counterGroup objects(XML) | A collection of counter group objects |
+| taskCounterGroup | array of counterGroup objects(JSON)/zero or more counterGroup objects(XML) | A collection of counter group objects |
 
 #### Elements of the *counterGroup* object