Bump alpine from 3.20.3 to 3.21.2

Bumps alpine from 3.20.3 to 3.21.2.

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

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

Author: dependabot[bot]

Dockerfile

@@ -1,5 +1,5 @@
 # Use a clean tiny image to store artifacts in
-FROM alpine:3.20.3
+FROM alpine:3.21.2
 
 # Labels for http://label-schema.org/rc1/#build-time-labels
 # And for https://github.com/opencontainers/image-spec/blob/master/annotations.md