cmd-list.perl: fix identifying man sections

We attribute each documentation text file to a man section by finding a line in the file that looks like "gitfoo(<digit>)". Commit cc75e556a9 ("scalar: add to 'git help -a' command list", 2022-09-02) updated this logic to look not only for "gitfoo" but also "scalarfoo". In doing so, it forgot to account for the fact that after the updated regex has found a match, the man section is no longer to be found in `$1` but now lives in `$2`. This makes our git(1) manpage look as follows: Main porcelain commands git-add(git) Add file contents to the index. [...] gitk(git) The Git repository browser. scalar(scalar) A tool for managing large Git repositories. Restore the man sections by not capturing the (git|scalar) part of the match into `$1`. As noted by Ævar [1], we could even match any "foo" rather than just "gitfoo" and "scalarfoo", but that's a larger change. For now, just fix the regression in cc75e556a9. [1] https://lore.kernel.org/git/220923.86wn9u4joo.gmgdl@evledraar.gmail.com/#t Helped-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com> Signed-off-by: Martin Ågren <martin.agren@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>