Use bookworm-backports suite for guessed distro

While Buster Backport should still be active, it currently falls under old-old-stable.

With debchange from the devscripts package in Bookworm, it reports an error for Buster, which is not reported with the release code name

$ debchange --no-conf -c "/tmp/changelog" --vendor Debian --create -D buster-backports --package test-package -v 1.0-1 'First upload'debchange warning: Recognised distributions are:
experimental, unstable, testing, stable, oldstable, oldoldstable,
{trixie,bookworm,bullseye,buster}-proposed-updates,
{testing,stable,oldstable,oldoldstable}-proposed-updates,
{trixie,bookworm,bullseye,buster}-security,
{testing,stable,oldstable,oldoldstable}}-security, bullseye-backports, bookworm-backports and UNRELEASED.
Using your request anyway.

Signed-off-by: Ritesh Raj Sarraf ritesh.sarraf@collabora.com