bisect: fix singular/plural grammar nit
bisect: fix singular/plural grammar nit

Remove the trailing 's' from "revisions" and "steps" when there is
only one.

Signed-off-by: David Ripton <4311da54442e41dcf296b11c919bbe45e2e63c9e@ripton.net>
Signed-off-by: Junio C Hamano <a6723cc3f76163bf7adb636a73ac3b0ceb3e6b9b@pobox.com>

destenson/git,destenson/git,destenson/git,destenson/git,destenson/git,destenson/git,destenson/git,destenson/git