chore(deps): update alpine docker tag to v3.21.2

roles/dagger/files/image/Dockerfile

@@ -1,11 +1,11 @@
-FROM alpine:3.18.4@sha256:eece025e432126ce23f223450a0326fbebde39cdf496a85d8c016293fc851978 as builder
+FROM alpine:3.21.2@sha256:56fa17d2a7e7f168a043a2712e63aed1f8543aeafdcee47c58dcffe38ed51099 as builder
 # renovate: datasource=github-releases depName=dagger lookupName=dagger/dagger versioning=npm
 ARG DAGGER_RELEASE_VERSION=v0.5.1
 WORKDIR /usr/local
 RUN apk add --no-cache curl bash
 # ${DAGGER_RELEASE_VERSION:1} drops v from the version
 RUN bash -c "export DAGGER_VERSION=${DAGGER_RELEASE_VERSION:1} && curl -L https://dl.dagger.io/dagger/install.sh | sh"
-FROM alpine:3.18.4@sha256:eece025e432126ce23f223450a0326fbebde39cdf496a85d8c016293fc851978
+FROM alpine:3.21.2@sha256:56fa17d2a7e7f168a043a2712e63aed1f8543aeafdcee47c58dcffe38ed51099
 COPY --from=builder /usr/local/bin/dagger /usr/local/bin/dagger
 COPY verify_version.sh .
 ENTRYPOINT [ "/usr/local/bin/dagger" ]