Update documentation surrounding extractFromJSON function and JSONToTuple operator

[nmwaara]

In recent discussions, we decided that adding a prefixToIgnore parameter to the extractFromJSON function would not be necessary if we added documentation describing how you can implement the same logic using the prefixToIgnore parameter of the JSONToTuple operator. We believe this is important to specify so that users do not get confused as to why there is no prefixToIgnore parameter for the extractFromJSON function.