chore(deps): bump debian in /dockerfiles/agent-discovery (#2178)

Bumps debian from bookworm-20250407-slim to bookworm-20260406-slim.

---
updated-dependencies:
- dependency-name: debian
  dependency-version: bookworm-20260406-slim
  dependency-type: direct:production
...

Signed-off-by: dependabot[bot] <[email protected]>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>
Co-authored-by: Bruno Verachten <[email protected]>

Author: dependabot[bot]

dockerfiles/agent-discovery/Dockerfile

@@ -1,7 +1,7 @@
 # This Dockerfile is used to prepare a Debian-based Docker image with several utilities installed.
 
 # We start from the Debian 'bookworm' image dated 2023-11-20.
-FROM debian:bookworm-20250407-slim as prepare-stage
+FROM debian:bookworm-20260406-slim as prepare-stage
 
 # Copy all shell scripts from the current directory to /usr/local/bin/ in the image.
 COPY *sh /usr/local/bin/