git-rebase--am: remove unnecessary --3way option

Since 22db240 (git-am: propagate --3way options as well, 2008-12-04),
the --3way has been propageted across failure, so it is since
pointless to pass it to git-am when resuming.

Signed-off-by: Martin von Zweigbergk <martin.von.zweigbergk@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Author: Martin von Zweigbergk

git-rebase--am.sh

@@ -7,12 +7,12 @@
 
 case "$action" in
 continue)
-	git am --resolved --3way --resolvemsg="$resolvemsg" &&
+	git am --resolved --resolvemsg="$resolvemsg" &&
 	move_to_original_branch
 	exit
 	;;
 skip)
-	git am --skip -3 --resolvemsg="$resolvemsg" &&
+	git am --skip --resolvemsg="$resolvemsg" &&
 	move_to_original_branch
 	exit
 	;;