chore(deps): update alpine docker tag to v3.21.1 (#553)

Co-authored-by: renovate[bot] <29139614+renovate[bot]@users.noreply.github.com>

Author: renovate[bot]

Dockerfile

@@ -7,7 +7,7 @@ FROM ghcr.io/uniget-org/tools/gh:2.64.0@sha256:488d0c020d42f4cb3626959ceeb73b617
 FROM ghcr.io/uniget-org/tools/gosec:2.21.4@sha256:40d6182efd001843aba8a74fc778dfad2cb0fb4d1c89ec25e3424a8ed2f63f66 AS uniget-gosec
 FROM ghcr.io/uniget-org/tools/golangci-lint:1.63.4@sha256:0fbf6af165633030827e37136259b55f79c98dd2f439169229482d2cedfa8d44 AS lint-base
 FROM golang:1.23.4@sha256:7ea4c9dcb2b97ff8ee80a67db3d44f98c8ffa0d191399197007d8459c1453041 AS latest-golang
-FROM alpine:3.21.0@sha256:21dc6063fd678b478f57c0e13f47560d0ea4eeba26dfc947b2a4f81f686b9f45 AS latest-alpine
+FROM alpine:3.21.1@sha256:b97e2a89d0b9e4011bb88c02ddf01c544b8c781acf1f4d559e7c8f12f1047ac3 AS latest-alpine
 FROM ubuntu:24.04@sha256:80dd3c3b9c6cecb9f1667e9290b3bc61b78c2678c02cbdae5f0fea92cc6734ab AS latest-ubuntu
 
 FROM --platform=${BUILDPLATFORM} latest-golang AS base