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>

Author: dependabot[bot]

Dockerfile

@@ -27,7 +27,7 @@ RUN go build -o /usr/local/bin/vault-secrets-webhook .
 RUN xx-verify /usr/local/bin/vault-secrets-webhook
 
 
-FROM alpine:3.20.3@sha256:1e42bbe2508154c9126d48c2b8a75420c3544343bf86fd041fb7527e017a4b4a
+FROM alpine:3.21.0@sha256:21dc6063fd678b478f57c0e13f47560d0ea4eeba26dfc947b2a4f81f686b9f45
 
 RUN apk add --update --no-cache ca-certificates tzdata libcap