doc: format-patch: fix typo
doc: format-patch: fix typo

reroll count documentation states that v<n> will be pretended to the
filename. Judging by the examples that should have been 'prepended'.

Signed-off-by: Frans Klaver <4cc5f7dfc6b9453b73d1fba73a574c3df56fb76e@gmail.com>
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