t9301: Add 2nd testcase exposing bugs in fast-import's notes fanout handling

t9301: Add 2nd testcase exposing bugs in fast-import's notes fanout handling

The previous patch exposed a bug in fast-import where _removing_ an existing
note fails (when that note resides on a non-zero fanout level, and was added
prior to this fast-import run).

This patch demostrates the same issue when _changing_ an existing note
(subject to the same circumstances).

Discovered-by: Henrik Grubbström <grubba@roxen.com>
Signed-off-by: Johan Herland <johan@herland.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>