remove ColorMode from next app

no longer required

Author: dburles

examples/next/pages/_app.js

@@ -1,6 +1,6 @@
 import React from 'react'
 import App from 'next/app'
-import { ThemeProvider, Styled, ColorMode } from 'theme-ui'
+import { ThemeProvider, Styled } from 'theme-ui'
 
 import Header from '../components/Header'
 import theme from '../src/theme'
@@ -22,7 +22,6 @@ class MyApp extends App {
     const { Component, pageProps } = this.props
     return (
       <ThemeProvider theme={theme}>
-        <ColorMode />
         <Header />
         <Styled.root>
           <Component {...pageProps} />