message: clean up MergeButton utility classes
diff: @@ -28,11 +28,11 @@ const MergeButton = ({numCommits, onClick, primary}) => {
  const commits = numCommits === 1 ? '1 commit' : `${numCommits} commits`
  return (
  - <div className="BtnGroup">
  + <div className="BtnGroup d-flex">
  <Button {...buttonSchemeProps} grouped onClick={onClick} css={{borderRight: 0}}>
  Merge Pull Request
  </Button>
  - <Details className="details-reset d-flex float-right">
  + <Details>
  {({toggle}) => (
  <React.Fragment>
  <Button is="summary" {...buttonSchemeProps} onClick={toggle} css={borderStyles}>
  