Small documentation fix (removed mention of non-existing aggregation function)
Small documentation fix (removed mention of non-existing aggregation function)

hermanbanken/RxScala,zhongdj/RxScala,jbripley/RxScala,hermanbanken/RxScala,zjrstar/RxScala,samuelgruetter/RxScala,jbripley/RxScala,samuelgruetter/RxScala,joohnnie/RxScala,TracyLu/RxScala,ReactiveX/RxScala