upgrade postfix package from v3.7.3-r1 to v3.7.4-r0 (see below)

https://web.archive.org/web/20230128075803/https://www.postfix.org/announcements/postfix-3.7.4.html
https://web.archive.org/web/20230128075530/https://git.alpinelinux.org/aports/commit/main/postfix?h=3.17-stable&id=137798230ca4204283aa92bf650826eb22c72b3f

Dockerfile

@@ -1,6 +1,6 @@
 FROM alpine:3.17.1
 
-ARG POSTFIX_PACKAGE_VERSION=3.7.3-r1
+ARG POSTFIX_PACKAGE_VERSION=3.7.4-r0
 # http://www.postfix.org/postconf.5.html#tls_append_default_CA
 # https://www.mozilla.org/en-US/about/governance/policies/security-group/certs/
 ARG MOZILLA_CA_CERT_STORE_PACKAGE_VERSION=20220614-r4