docs: don't mention --quiet or --exit-code in git-log(1)

These are diff-options, but they don't actually make sense
in the context of log.

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Documentation/diff-options.txt

@@ -409,6 +409,7 @@ endif::git-format-patch[]
 	of lines, thereby fusing hunks that are close to each other.
 
 ifndef::git-format-patch[]
+ifndef::git-log[]
 --exit-code::
 	Make the program exit with codes similar to diff(1).
 	That is, it exits with 1 if there were differences and
@@ -416,6 +417,7 @@ ifndef::git-format-patch[]
 
 --quiet::
 	Disable all output of the program. Implies `--exit-code`.
+endif::git-log[]
 endif::git-format-patch[]
 
 --ext-diff::