chore(deps): update alpine docker tag to v3.21

Signed-off-by: Renovate Bot <[email protected]>

Author: renovate[bot]

Containerfile

@@ -30,7 +30,7 @@ RUN apt-get update \
     && python3 /defaults.py \
     && python3 /generator.py
 
-FROM alpine:3.18
+FROM alpine:3.21
 COPY --from=cue-builder /build/bin/cue /bin/cue
 COPY --from=cue-definition-generator /output /definitions