prvTaskCheckFreeStackSpace remove redundant cast #11

Job	Run time
build (examples/AnalogRead_DigitalRead/AnalogRead_DigitalRead.ino)	24s
build (examples/ArrayQueue/ArrayQueue.ino)	23s
build (examples/Assert/Assert.ino)	23s
build (examples/Blink_AnalogRead/Blink_AnalogRead.ino)	22s
build (examples/IntegerQueue/IntegerQueue.ino)	27s
build (examples/Interrupts/Interrupts.ino)	28s
build (examples/Mutex/Mutex.ino)	27s
build (examples/Notifications/Notifications.ino)	28s
build (examples/StructArray/StructArray.ino)	28s
build (examples/StructQueue/StructQueue.ino)	25s
build (examples/TaskStatus/TaskStatus.ino)	22s
build (examples/TaskUtilities/TaskUtilities.ino)	22s
	4m 59s

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