fix: remove unused code

Author: gregberge

packages/styled-components/src/Box.js

@@ -14,5 +14,4 @@ export {
 
 export { css } from './css'
 export { createGlobalStyle } from './createGlobalStyle'
-export { Box } from './Box'
-export { styled as default } from './styled'
+export { Box, styled as default } from './styled'

packages/styled-components/src/Box.test.js

@@ -38,7 +38,7 @@ const createBoxComponent = component => ({ as, ...props }) => {
   return <Component {...omittedProps} />
 }
 
-const Box = styled(createBoxComponent('div'))(createBox)
+export const Box = styled(createBoxComponent('div'))(createBox)
 
 styled.box = styled(Box)