These links should point to `.html` files, not to `.txt` ones.
Compare also to 4945f046c7 (api docs: link to html version of
api-trace2, 2022-09-16).
Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>