fix: build/windows/Dockerfile to reduce vulnerabilities (#5913)

The following vulnerabilities are fixed with an upgrade:
- https://snyk.io/vuln/SNYK-ALPINE313-APKTOOLS-1533754
- https://snyk.io/vuln/SNYK-ALPINE313-OPENSSL-1089239
- https://snyk.io/vuln/SNYK-ALPINE313-OPENSSL-1569446
- https://snyk.io/vuln/SNYK-ALPINE313-OPENSSL-1569448
- https://snyk.io/vuln/SNYK-ALPINE313-OPENSSL-1569448

build/windows/Dockerfile

@@ -1,6 +1,6 @@
 ARG OSVERSION
 FROM --platform=linux/amd64 gcr.io/k8s-staging-e2e-test-images/windows-servercore-cache:1.0-linux-amd64-${OSVERSION} as core
-FROM --platform=linux/amd64 alpine:3.13.0 as downloader
+FROM --platform=linux/amd64 alpine:3.14 as downloader
 ENV GIT_VERSION 2.30.0
 ENV GIT_PATCH_VERSION 2