build(deps): bump alpine from 3.20.3 to 3.21.0

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] <support@github.com>

Dockerfile

@@ -35,13 +35,13 @@ RUN make release-binary
 
 RUN xx-verify /go/bin/dex && xx-verify /go/bin/docker-entrypoint
 
-FROM alpine:3.20.3@sha256:1e42bbe2508154c9126d48c2b8a75420c3544343bf86fd041fb7527e017a4b4a AS stager
+FROM alpine:3.21.0@sha256:21dc6063fd678b478f57c0e13f47560d0ea4eeba26dfc947b2a4f81f686b9f45 AS stager
 
 RUN mkdir -p /var/dex
 RUN mkdir -p /etc/dex
 COPY config.docker.yaml /etc/dex/
 
-FROM alpine:3.20.3@sha256:1e42bbe2508154c9126d48c2b8a75420c3544343bf86fd041fb7527e017a4b4a AS gomplate
+FROM alpine:3.21.0@sha256:21dc6063fd678b478f57c0e13f47560d0ea4eeba26dfc947b2a4f81f686b9f45 AS gomplate
 
 ARG TARGETOS
 ARG TARGETARCH
@@ -54,7 +54,7 @@ RUN wget -O /usr/local/bin/gomplate \
   && chmod +x /usr/local/bin/gomplate
 
 # For Dependabot to detect base image versions
-FROM alpine:3.20.3@sha256:1e42bbe2508154c9126d48c2b8a75420c3544343bf86fd041fb7527e017a4b4a AS alpine
+FROM alpine:3.21.0@sha256:21dc6063fd678b478f57c0e13f47560d0ea4eeba26dfc947b2a4f81f686b9f45 AS alpine
 FROM gcr.io/distroless/static-debian12:nonroot@sha256:d71f4b239be2d412017b798a0a401c44c3049a3ca454838473a4c32ed076bfea AS distroless
 
 FROM $BASE_IMAGE