This partially reverts [35738], which has shown to provide a bad user experience for users seeking to experiment with TwentySeventeen.
This will result in TwentySixteen being installed in addition to TwentySeventeen.
See #38551.
git-svn-id: https://develop.svn.wordpress.org/trunk@39064 602fd350-edb4-49c9-b593-d223f7449a82