Bump alpine from 3.20 to 3.21 in /package

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>

package/Dockerfile

@@ -1,4 +1,4 @@
-FROM alpine:3.20
+FROM alpine:3.21
 ARG ARCH=amd64
 COPY dist/artifacts/kine-${ARCH} /bin/kine
 RUN mkdir /db && chown nobody /db