upgrade alpine base image from v3.19.1 to v3.20.0. including upgrade of

postfix package from v3.8.6-r0 to v3.9.0-r1

https://web.archive.org/web/20240525192630/https://www.postfix.org/announcements/postfix-3.9.0.html
https://web.archive.org/web/20240525192515/https://git.alpinelinux.org/aports/commit/main/postfix?h=3.20-stable&id=7edd2c862768f0bf31a44364e3b9785cfa387f15
https://web.archive.org/web/20240525192519/https://git.alpinelinux.org/aports/commit/main/postfix?h=3.20-stable&id=3b409e13c526a955f4d13c629f2f2535d3eb5adf

Dockerfile

@@ -1,8 +1,8 @@
-FROM docker.io/alpine:3.19.1
+FROM docker.io/alpine:3.20.0
 
 # http://www.postfix.org/announcements.html
-# https://git.alpinelinux.org/aports/log/main/postfix?h=3.19-stable
+# https://git.alpinelinux.org/aports/log/main/postfix?h=3.20-stable
-ARG POSTFIX_PACKAGE_VERSION=3.8.6-r0
+ARG POSTFIX_PACKAGE_VERSION=3.9.0-r1
 # http://www.postfix.org/postconf.5.html#tls_append_default_CA
 # https://www.mozilla.org/en-US/about/governance/policies/security-group/certs/
 # https://gitlab.alpinelinux.org/alpine/ca-certificates/-/commits/master