build(deps): bump alpine from 3.20 to 3.21 (#1151)

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>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Dockerfile

@@ -26,7 +26,7 @@ ADD . /app
 ARG CSB_VERSION=0.0.0
 RUN CGO_CFLAGS="-D_LARGEFILE64_SOURCE" CGO_ENABLED=1 GOOS=linux go build -o ./build/cloud-service-broker -ldflags "-X github.com/cloudfoundry/cloud-service-broker/utils.Version=$CSB_VERSION"
 
-FROM alpine:3.20
+FROM alpine:3.21
 
 COPY --from=build /app/build/cloud-service-broker /bin/cloud-service-broker