Fix unit tests (#2428)

* only create toaster if we're on the browser

* drop/fix references to window

* add back fe unit tests

client/__tests__/util/annoMatrix/serverMocks/index.js

@@ -1,11 +1,4 @@
 export const baseDataURL = "https://a.fake.url/api/v0.2";
 
-window.CELLXGENE = {
-  API: {
-    prefix: baseDataURL,
-    version: "v0.2/",
-  },
-};
-
 export { schema } from "./schema";
 export * from "./routes";