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] <[email protected]>

Dockerfile

@@ -25,7 +25,7 @@ RUN CGO_ENABLED=1 \
              ./cmd/shell-operator
 
 # Final image
-FROM --platform=${TARGETPLATFORM:-linux/amd64} alpine:3.20
+FROM --platform=${TARGETPLATFORM:-linux/amd64} alpine:3.21
 ARG TARGETPLATFORM
 RUN apk --no-cache add ca-certificates bash sed tini && \
     kubectlArch=$(echo ${TARGETPLATFORM:-linux/amd64} | sed 's/\/v7//') && \