Bump alpine from 3.13 to 3.14 in /build (#2021)

Bumps alpine from 3.13 to 3.14.

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

Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Author: dependabot[bot]

build/Dockerfile

@@ -25,7 +25,7 @@ RUN apk add --no-cache libcap \
 
 
 ############################################# Base image for Alpine with NGINX Plus #############################################
-FROM alpine:3.13 as alpine-plus
+FROM alpine:3.14 as alpine-plus
 ARG NGINX_PLUS_VERSION
 
 RUN --mount=type=secret,id=nginx-repo.crt,dst=/etc/apk/cert.pem,mode=0644 \