help: make auto-correction prompt more consistent

help: make auto-correction prompt more consistent

There are three callsites of git_prompt() helper function that ask a
"yes/no" question to the end user, but one of them in help.c that
asks if the suggested auto-correction is OK, which is given when the
user makes a possible typo in a Git subcommand name, is formatted
differently from the others.

Update the format string to make the prompt string look more
consistent.

Signed-off-by: Kashav Madan <kshvmdn@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>