Update JMX metric name in documentation

[oneonestar]

Description

Update JMX metric name

Non-technical explanation

TaskManager has been refactored to SqlTaskManager since version 372.
78cb3d5

Verify:

# HELP trino_execution_SqlTaskManager_InputPositions_FifteenMinute_Count  trino.execution:name=SqlTaskManager,type=null,attribute=InputPositions.FifteenMinute.Count
# TYPE trino_execution_SqlTaskManager_InputPositions_FifteenMinute_Count untyped
trino_execution_SqlTaskManager_InputPositions_FifteenMinute_Count 0.0

# HELP trino_execution_SqlTaskManager_InputDataSize_TotalCount  trino.execution:name=SqlTaskManager,type=null,attribute=InputDataSize.TotalCount
# TYPE trino_execution_SqlTaskManager_InputDataSize_TotalCount untyped
trino_execution_SqlTaskManager_InputDataSize_TotalCount 0.0
...

Release notes

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( ) Release notes are required, with the following suggested text:

# Section
* Fix some things. ({issue}`issuenumber`)