Bump debian from 11.3-slim to 11.4-slim in /.ci/docker-ci/debian-gnupg2 (#900)

Bumps debian from 11.3-slim to 11.4-slim.

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

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Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

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

@@ -1,4 +1,4 @@
-FROM debian:11.3-slim
+FROM debian:11.4-slim
 
 LABEL maintainer="mail@sobolevn.me"
 LABEL vendor="git-secret team"