Fix setup wizard test lint errors

frontend/src/metabase/setup/components/DatabaseConnectionStep.jsx

 /* eslint "react/prop-types": "warn" */
 import React, { Component } from "react";
 import PropTypes from "prop-types";
-import ReactDOM from "react-dom";
 
 import StepTitle from './StepTitle.jsx'
 import CollapsedStep from "./CollapsedStep.jsx";

frontend/test/setup/signup.integ.spec.js

@@ -23,7 +23,7 @@ import {
 import path from "path";
 import { mount } from "enzyme";
 import Setup from "metabase/setup/components/Setup";
-import { delay } from "metabase/lib/promise";
+import { delay } from "metabase/lib/promise";
 import UserStep from "metabase/setup/components/UserStep";
 import DatabaseConnectionStep from "metabase/setup/components/DatabaseConnectionStep";
 import PreferencesStep from "metabase/setup/components/PreferencesStep";