CI: Pin shellcheck on bookworm to a different version

.gitlab/ci/ci-templates.gitlab-ci.yml

@@ -9,5 +9,6 @@ templates-shellcheck:
   needs:
     - setup-test-env
   script:
-    - apt update && apt install -y shellcheck=0.7.1-1+deb11u1
+    # Try bullseye (0.7) first and then bookworm (0.9)
+    - apt update && apt install -y shellcheck=0.7.1-1+deb11u1 || apt install -y shellcheck=0.9.0-1
     - bundle exec scripts/lint_templates_bash.rb