upgrade alpine base image from v3.20.3 to v3.21.0 including upgrade of socat package (links below)

https://web.archive.org/web/20241207112827/http://www.dest-unreach.org/socat/CHANGES
https://git.alpinelinux.org/aports/commit/main/socat?h=3.21-stable&id=a429740484f9c5543597f5f209935745987a4626

Dockerfile

@@ -1,11 +1,11 @@
-FROM docker.io/alpine:3.20.3
+FROM docker.io/alpine:3.21.0
 
 # https://dovecot.org/doc/NEWS
-# https://git.alpinelinux.org/aports/log/main/dovecot?h=3.20-stable
+# https://git.alpinelinux.org/aports/log/main/dovecot?h=3.21-stable
 ARG DOVECOT_PACKAGE_VERSION=2.3.21.1-r0
 # http://www.dest-unreach.org/socat/
-# https://git.alpinelinux.org/aports/log/main/socat?h=3.20-stable
-ARG SOCAT_PACKAGE_VERSION=1.8.0.0-r0
+# https://git.alpinelinux.org/aports/log/main/socat?h=3.21-stable
+ARG SOCAT_PACKAGE_VERSION=1.8.0.1-r0
 RUN apk add --no-cache \
         dovecot-lmtpd=$DOVECOT_PACKAGE_VERSION \
         dovecot-pigeonhole-plugin=$DOVECOT_PACKAGE_VERSION \