format-patch documentation: Remove diff options that are not useful

To simplify reading the documentation for format-patch, remove the
description of common diff options that are not useful for the
purpose of the command (i.e. "Prepare patches for e-mail submission").

Specifically, this removes the description of the following options:

--raw
-z
--color
--no-color
--color-words
--diff-filter
-S
--pickaxe-all
--pickaxe-regex
-R
--relative
--exit-code
--quiet

Signed-off-by: Björn Gustavsson <bgustavsson@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>