Apply suggestions from referee

.gitlab-ci.yml

 precommit:
-  image: python:slim-bullseye
+  image: python:slim-bookworm
   before_script:
     - apt update && apt install -y --no-install-recommends git
     - pip install -r requirements.txt

.pre-commit-config.yaml

-# See https://pre-commit.com for more information
-# See https://pre-commit.com/hooks.html for more hooks
 repos:
 -   repo: https://github.com/pre-commit/pre-commit-hooks
     rev: v4.6.0