build: bump library/alpine from 3.21.1 to 3.21.2

Bumps library/alpine from 3.21.1 to 3.21.2.

---
updated-dependencies:
- dependency-name: library/alpine
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

Signed-off-by: dependabot[bot] <[email protected]>

Author: dependabot[bot]

Dockerfile

@@ -1,6 +1,6 @@
 FROM docker.io/nginxproxy/docker-gen:0.14.4 AS docker-gen
 
-FROM docker.io/library/alpine:3.21.1
+FROM docker.io/library/alpine:3.21.2
 
 ARG GIT_DESCRIBE="unknown"
 ARG ACMESH_VERSION=3.1.0