chore(deps): bump alpine from 3.20 to 3.21

Bumps alpine from 3.20 to 3.21.

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

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

Dockerfile

@@ -17,7 +17,7 @@ RUN GOOS=$TARGETOS GOARCH=$TARGETARCH goreleaser build --snapshot="${BUILD_SNAPS
 ##
 ## Runtime
 ##
-FROM alpine:3.20
+FROM alpine:3.21
 
 LABEL "steadybit.com.discovery-disabled"="true"