build(deps): bump library/alpine from 3.20 to 3.21 in the docker group

Bumps the docker group with 1 update: library/alpine.


Updates `library/alpine` from 3.20 to 3.21

---
updated-dependencies:
- dependency-name: library/alpine
  dependency-type: direct:production
  update-type: version-update:semver-minor
  dependency-group: docker
...

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

Dockerfile

@@ -43,7 +43,7 @@ RUN set -x \
     && /tmp/error-pages -h
 
 # -✂- this stage is used to prepare the runtime fs --------------------------------------------------------------------
-FROM docker.io/library/alpine:3.20 AS rootfs
+FROM docker.io/library/alpine:3.21 AS rootfs
 
 WORKDIR /tmp/rootfs