Bump debian from 11-slim to 12-slim

Bumps debian from 11-slim to 12-slim.

---
updated-dependencies:
- dependency-name: debian
  dependency-type: direct:production
...

Signed-off-by: dependabot[bot] <[email protected]>

Author: dependabot[bot]

Dockerfile

@@ -1,6 +1,6 @@
 # Buildbot master and master-web containers
 
-FROM debian:11-slim
+FROM debian:12-slim
 LABEL maintainer="MariaDB Buildbot maintainers"
 ARG DEBIAN_FRONTEND=noninteractive
 ARG master_type="master"