chore: bump alpine from 3.18.2 to 3.21.3

Bumps alpine from 3.18.2 to 3.21.3.

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

Signed-off-by: dependabot[bot] <[email protected]>

Author: dependabot[bot]

Dockerfile

@@ -10,7 +10,7 @@ WORKDIR /usr/src/k8s-rdma-shared-dp
 RUN make clean && \
     make build
 
-FROM alpine:3.18.2
+FROM alpine:3.21.3
 RUN apk add --no-cache kmod=30-r3 hwdata-pci=0.370-r0
 COPY --from=builder /usr/src/k8s-rdma-shared-dp/build/k8s-rdma-shared-dp /bin/