build(deps): Bump alpine

Bumps the docker group with 1 update in the /.release directory: alpine.


Updates `alpine` from 3.18 to 3.21

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

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

.release/alpine.Dockerfile

@@ -1,4 +1,4 @@
-FROM alpine:3.18
+FROM alpine:3.21
 
 RUN apk --no-cache add \
       ca-certificates \