fix(db-functions): Add package signatures back to repo desc files

With pacman 6.1 the addition of package signatures to the repository
sync database "desc" file has been demoted to the `--include-sigs`
options.

We want signatures in our sync database because it allows us to search
for signer of a package using `pacman -Sii`.

Signed-off-by: David Runge <dvzrv@archlinux.org>