🌱 Update Cspo Image group to v3.21.3

| datasource | package                  | from   | to     |
| ---------- | ------------------------ | ------ | ------ |
| docker     | docker.io/library/alpine | 3.21.2 | 3.21.3 |

Author: cluster-stack-bot[bot]

images/cspo/Dockerfile

@@ -23,7 +23,7 @@ RUN --mount=type=cache,target=/root/.cache --mount=type=cache,target=/go/pkg \
     go build -mod=vendor -trimpath -ldflags "-s -w ${LDFLAGS} -extldflags '-static'" \
     -o manager cmd/main.go
 
-FROM --platform=${BUILDPLATFORM} docker.io/library/alpine:3.21.2
+FROM --platform=${BUILDPLATFORM} docker.io/library/alpine:3.21.3
 WORKDIR /
 COPY --from=build /src/cluster-stack-provider-openstack/manager .