dev-cmd/tap-new: fix output on newer versions of Git.
dev-cmd/tap-new: fix output on newer versions of Git.

Otherwise this prints to `stderr` to ask for configuration of the branch
name:
https://github.com/Homebrew/brew/pull/10323/checks?check_run_id=1701105141#step:5:51

vitorgalvao/brew,sjackman/homebrew,EricFromCanada/brew,nandub/brew,Homebrew/brew,claui/brew,EricFromCanada/brew,sjackman/homebrew,EricFromCanada/brew,sjackman/homebrew,vitorgalvao/brew,JCount/brew,Homebrew/brew,claui/brew,JCount/brew,MikeMcQuaid/brew,Homebrew/brew,JCount/brew,MikeMcQuaid/brew,MikeMcQuaid/brew,Homebrew/brew,vitorgalvao/brew,claui/brew,vitorgalvao/brew,nandub/brew,MikeMcQuaid/brew,JCount/brew,claui/brew,nandub/brew,sjackman/homebrew,nandub/brew,EricFromCanada/brew