Bump debian from 11.7-slim to 12.5-slim in /.ci/docker-ci/debian-gnupg2

Bumps debian from 11.7-slim to 12.5-slim.

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

Signed-off-by: dependabot[bot] <support@github.com>

.ci/docker-ci/debian-gnupg2/Dockerfile

@@ -1,4 +1,4 @@
-FROM debian:11.7-slim
+FROM debian:12.5-slim
 
 LABEL maintainer="mail@sobolevn.me"
 LABEL vendor="git-secret team"