Bump alpine from 3.20 to 3.21 in the dev-dependencies group

Bumps the dev-dependencies group with 1 update: alpine.


Updates `alpine` from 3.20 to 3.21

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

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

Dockerfile

@@ -22,7 +22,7 @@ RUN CGO_ENABLED=0 GOOS=linux GOARCH=amd64 go build -a -o manager main.go
 
 # Use distroless as minimal base image to package the manager binary
 # Refer to https://github.com/GoogleContainerTools/distroless for more details
-FROM alpine:3.20
+FROM alpine:3.21
 WORKDIR /
 COPY --from=builder /workspace/manager .
 USER 65532:65532