Bump alpine from 3.20.3 to 3.21.1

Bumps alpine from 3.20.3 to 3.21.1.

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

Signed-off-by: dependabot[bot] <support@github.com>

Dockerfile

@@ -1,4 +1,4 @@
-FROM alpine:3.20.3@sha256:beefdbd8a1da6d2915566fde36db9db0b524eb737fc57cd1367effd16dc0d06d
+FROM alpine:3.21.1@sha256:b97e2a89d0b9e4011bb88c02ddf01c544b8c781acf1f4d559e7c8f12f1047ac3
 
 LABEL repository="https://github.com/is-cool-me/dnscontrol-action"
 LABEL maintainer="light <admin@lighthosting.eu.org>"