upgrade alpine base image v3.12.3->3.13.0 including upgrade of ca-certificates package (postfix unchanged)

Dockerfile

@@ -1,9 +1,9 @@
-FROM alpine:3.12.3
+FROM alpine:3.13.0
 
 ARG POSTFIX_PACKAGE_VERSION=3.5.8-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=20191127-r4
+ARG MOZILLA_CA_CERT_STORE_PACKAGE_VERSION=20191127-r5
 RUN apk add --no-cache \
         ca-certificates=$MOZILLA_CA_CERT_STORE_PACKAGE_VERSION \
         postfix=$POSTFIX_PACKAGE_VERSION \