Fix typo in `_.iteratee` docs
Fix typo in `_.iteratee` docs

jdelbello/underscore,tnga/underscore-es,keepgoingwm/underscore,rlugojr/underscore,akre54/underscore,keepgoingwm/underscore,jdelbello/underscore,tnga/underscore-es,jashkenas/underscore,rlugojr/underscore,jashkenas/underscore,documentcloud/underscore,akre54/underscore,documentcloud/underscore