pgsql: ci: Upgrade to Debian Bookworm

ci: Upgrade to Debian Bookworm

Bullseye is getting long in the tooth, upgrade to the current stable version.

Backpatch to all versions with CI support, we don't want to generate CI images
for multiple Debian versions.

Author: Nazir Bilal Yavuz <byavuz81@gmail.com>
Discussion: https://postgr.es/m/CAN55FZ0fY5EFHXLKCO_%3Dp4pwFmHRoVom_qSE_7B48gpchfAqzw%40mail.gmail.com
Backpatch: 15-, where CI was added

Branch
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REL_15_STABLE

Details
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https://git.postgresql.org/pg/commitdiff/27004d671162283840972113dbc7a22960cbbb07

Modified Files
--------------
.cirrus.tasks.yml | 8 ++++----
1 file changed, 4 insertions(+), 4 deletions(-)