angularjs: allow $q.when to be called w/o args

The current definition does not cover the case that the input type is void.
test failed again: https://travis-ci.org/borisyankov/DefinitelyTyped/builds/30457950

add `nothing` here https://github.com/xi/DefinitelyTyped/blob/feature-angularjs-when-void/angularjs/angular-tests.ts#L93-L98