Remove reference to crossfilter

As per:
https://github.com/DefinitelyTyped/DefinitelyTyped/issues/26548

types/dc/dc-tests.ts

@@ -1,3 +1,8 @@
+import * as CrossFilter from 'crossfilter';
+import * as d3 from "d3";
+import * as dc from "dc";
+
+
 interface IYelpData {
     city: string;
     review_count: number;

types/dc/index.d.ts

@@ -5,10 +5,6 @@
 //                 matthias jobst <https://github.com/MatthiasJobst>
 // Definitions: https://github.com/DefinitelyTyped/DefinitelyTyped
 
-// this makes only sense together with d3 and crossfilter so you need the d3.d.ts and crossfilter.d.ts files
-
-///<reference types="crossfilter" />
-
 import * as d3 from "d3";
 
 export = dc;