doc: add some missing technical documents

Commit bcf7edee09 ("meson: generate articles", 2024-12-27) added the
generation of the 'howto' and 'technical' documents to the meson build.
At this time those documents had a '*.txt' file extension, but they were
renamed with an '*.adoc' extension by commit 1f010d6bdf ("doc: use .adoc
extension for AsciiDoc files", 2025-01-20), for the most part. For the
meson build, commit 87eccc3a81 ("meson: fix building technical and howto
docs", 2025-03-02) fixed the meson.build files, which had not been
updated when the files were renamed.

However, the 'Documentation/Makefile' has not been updated to include
all of the recently added technical documents. In particular, the
following are built by meson, but not by the Makefile:

commit-graph.adoc
directory-rename-detection.adoc
packfile-uri.adoc
remembering-renames.adoc
repository-version.adoc
rerere.adoc
sparse-checkout.adoc
sparse-index.adoc

In order to ensure that both build systems format the same technical
documents, add the above documents to the TECH_DOCS variable in the
Documentation/Makefile.

Signed-off-by: Ramsay Jones <ramsay@ramsayjones.plus.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>