hack(authors): bump to alpine 3.20

Signed-off-by: CrazyMax <1951866+crazy-max@users.noreply.github.com>

hack/dockerfiles/authors.Dockerfile

@@ -1,20 +1,21 @@
 # syntax=docker/dockerfile:1
 
-FROM alpine:3.14 AS gen
+ARG ALPINE_VERSION=3.20
+
+FROM alpine:${ALPINE_VERSION} AS gen
 RUN apk add --no-cache git
 WORKDIR /src
 RUN --mount=type=bind,target=. <<EOT
-#!/usr/bin/env bash
-set -e
-mkdir /out
-# see also ".mailmap" for how email addresses and names are deduplicated
-{
+  set -e
+  mkdir /out
+  # see also ".mailmap" for how email addresses and names are deduplicated
+  {
     echo "# This file lists all individuals having contributed content to the repository."
     echo "# For how it is generated, see hack/dockerfiles/authors.Dockerfile."
     echo
     git log --format='%aN <%aE>' | LC_ALL=C.UTF-8 sort -uf
-} > /out/AUTHORS
-cat /out/AUTHORS
+  } > /out/AUTHORS
+  cat /out/AUTHORS
 EOT
 
 FROM scratch AS update
@@ -22,12 +23,12 @@ COPY --from=gen /out /
 
 FROM gen AS validate
 RUN --mount=type=bind,target=.,rw <<EOT
-set -e
-git add -A
-cp -rf /out/* .
-if [ -n "$(git status --porcelain -- AUTHORS)" ]; then
+  set -e
+  git add -A
+  cp -rf /out/* .
+  if [ -n "$(git status --porcelain -- AUTHORS)" ]; then
     echo >&2 'ERROR: Authors result differs. Please update with "make authors"'
     git status --porcelain -- AUTHORS
     exit 1
-fi
+  fi
 EOT