docker: cli: bump alpine from 3.20.3 to 3.21.0 in /cli

Bumps alpine from 3.20.3 to 3.21.0.

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

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

cli/Dockerfile

@@ -49,6 +49,6 @@ RUN go build
 ENTRYPOINT ["/entrypoint-dev.sh"]
 
 # production stage
-FROM alpine:3.20.3 AS production
+FROM alpine:3.21.0 AS production
 
 COPY --from=builder /go/src/github.com/shellhub-io/shellhub/cli/cli /cli